Corrected the error

.flutter-plugins-dependencies

@@ -0,0 +1 @@
+{"info":"This is a generated file; do not edit or check into version control.","plugins":{"ios":[{"name":"firebase_auth","path":"/home/harsh/Flutter-SDK/flutter/.pub-cache/hosted/pub.dartlang.org/firebase_auth-0.10.0+1/","dependencies":["firebase_core"]},{"name":"firebase_core","path":"/home/harsh/Flutter-SDK/flutter/.pub-cache/hosted/pub.dartlang.org/firebase_core-0.4.0+6/","dependencies":[]},{"name":"google_sign_in","path":"/home/harsh/Flutter-SDK/flutter/.pub-cache/hosted/pub.dartlang.org/google_sign_in-4.0.2/","dependencies":[]}],"android":[{"name":"firebase_auth","path":"/home/harsh/Flutter-SDK/flutter/.pub-cache/hosted/pub.dartlang.org/firebase_auth-0.10.0+1/","dependencies":["firebase_core"]},{"name":"firebase_core","path":"/home/harsh/Flutter-SDK/flutter/.pub-cache/hosted/pub.dartlang.org/firebase_core-0.4.0+6/","dependencies":[]},{"name":"google_sign_in","path":"/home/harsh/Flutter-SDK/flutter/.pub-cache/hosted/pub.dartlang.org/google_sign_in-4.0.2/","dependencies":[]}],"macos":[],"linux":[],"windows":[],"web":[]},"dependencyGraph":[{"name":"firebase_auth","dependencies":["firebase_core"]},{"name":"firebase_core","dependencies":[]},{"name":"google_sign_in","dependencies":[]}],"date_created":"2020-07-24 10:13:38.908878","version":"1.21.0-1.0.pre"}

ios/Flutter/flutter_export_environment.sh

@@ -0,0 +1,15 @@
+#!/bin/sh
+# This is a generated file; do not edit or check into version control.
+export "FLUTTER_ROOT=/home/harsh/Flutter-SDK/flutter"
+export "FLUTTER_APPLICATION_PATH=/home/harsh/VS-Code/firebase_email_signin"
+export "FLUTTER_TARGET=lib/main.dart"
+export "FLUTTER_BUILD_DIR=build"
+export "SYMROOT=${SOURCE_ROOT}/../build/ios"
+export "OTHER_LDFLAGS=$(inherited) -framework Flutter"
+export "FLUTTER_FRAMEWORK_DIR=/home/harsh/Flutter-SDK/flutter/bin/cache/artifacts/engine/ios"
+export "FLUTTER_BUILD_NAME=1.0.0"
+export "FLUTTER_BUILD_NUMBER=1"
+export "DART_OBFUSCATION=false"
+export "TRACK_WIDGET_CREATION=false"
+export "TREE_SHAKE_ICONS=false"
+export "PACKAGE_CONFIG=.packages"

lib/pages/registration_page.dart

@@ -202,8 +202,8 @@ class _RegistrationPageState extends State<RegistrationPage> {
 
   Future<FirebaseUser> signUp(email, password) async {
     try {
-      FirebaseUser user = await auth.createUserWithEmailAndPassword(
-          email: email, password: password);
+      FirebaseUser user = (await auth.createUserWithEmailAndPassword(
+          email: email, password: password)).user;
       assert(user != null);
       assert(await user.getIdToken() != null);
       return user;

pubspec.lock

@@ -1,41 +1,62 @@
 # Generated by pub
-# See https://www.dartlang.org/tools/pub/glossary#lockfile
+# See https://dart.dev/tools/pub/glossary#lockfile
 packages:
   async:
     dependency: transitive
     description:
       name: async
       url: "https://pub.dartlang.org"
     source: hosted
-    version: "2.1.0"
+    version: "2.4.2"
   boolean_selector:
     dependency: transitive
     description:
       name: boolean_selector
       url: "https://pub.dartlang.org"
     source: hosted
-    version: "1.0.4"
+    version: "2.0.0"
+  characters:
+    dependency: transitive
+    description:
+      name: characters
+      url: "https://pub.dartlang.org"
+    source: hosted
+    version: "1.1.0-nullsafety"
   charcode:
     dependency: transitive
     description:
       name: charcode
       url: "https://pub.dartlang.org"
     source: hosted
-    version: "1.1.2"
+    version: "1.1.3"
+  clock:
+    dependency: transitive
+    description:
+      name: clock
+      url: "https://pub.dartlang.org"
+    source: hosted
+    version: "1.0.1"
   collection:
     dependency: transitive
     description:
       name: collection
       url: "https://pub.dartlang.org"
     source: hosted
-    version: "1.14.11"
+    version: "1.15.0-nullsafety"
   cupertino_icons:
     dependency: "direct main"
     description:
       name: cupertino_icons
       url: "https://pub.dartlang.org"
     source: hosted
     version: "0.1.2"
+  fake_async:
+    dependency: transitive
+    description:
+      name: fake_async
+      url: "https://pub.dartlang.org"
+    source: hosted
+    version: "1.1.0"
   firebase_auth:
     dependency: "direct main"
     description:
@@ -73,35 +94,21 @@ packages:
       name: matcher
       url: "https://pub.dartlang.org"
     source: hosted
-    version: "0.12.5"
+    version: "0.12.8"
   meta:
     dependency: transitive
     description:
       name: meta
       url: "https://pub.dartlang.org"
     source: hosted
-    version: "1.1.6"
+    version: "1.3.0-nullsafety"
   path:
     dependency: transitive
     description:
       name: path
       url: "https://pub.dartlang.org"
     source: hosted
-    version: "1.6.2"
-  pedantic:
-    dependency: transitive
-    description:
-      name: pedantic
-      url: "https://pub.dartlang.org"
-    source: hosted
-    version: "1.5.0"
-  quiver:
-    dependency: transitive
-    description:
-      name: quiver
-      url: "https://pub.dartlang.org"
-    source: hosted
-    version: "2.0.2"
+    version: "1.7.0"
   sky_engine:
     dependency: transitive
     description: flutter
@@ -113,14 +120,14 @@ packages:
       name: source_span
       url: "https://pub.dartlang.org"
     source: hosted
-    version: "1.5.5"
+    version: "1.7.0"
   stack_trace:
     dependency: transitive
     description:
       name: stack_trace
       url: "https://pub.dartlang.org"
     source: hosted
-    version: "1.9.3"
+    version: "1.9.5"
   stream_channel:
     dependency: transitive
     description:
@@ -134,7 +141,7 @@ packages:
       name: string_scanner
       url: "https://pub.dartlang.org"
     source: hosted
-    version: "1.0.4"
+    version: "1.0.5"
   term_glyph:
     dependency: transitive
     description:
@@ -148,21 +155,21 @@ packages:
       name: test_api
       url: "https://pub.dartlang.org"
     source: hosted
-    version: "0.2.4"
+    version: "0.2.17"
   typed_data:
     dependency: transitive
     description:
       name: typed_data
       url: "https://pub.dartlang.org"
     source: hosted
-    version: "1.1.6"
+    version: "1.3.0-nullsafety"
   vector_math:
     dependency: transitive
     description:
       name: vector_math
       url: "https://pub.dartlang.org"
     source: hosted
-    version: "2.0.8"
+    version: "2.1.0-nullsafety"
 sdks:
-  dart: ">=2.2.0 <3.0.0"
+  dart: ">=2.9.0-18.0 <2.9.0"
   flutter: ">=1.5.0 <2.0.0"