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+      "../../lodash/_insertWrapDetails.js": 1103,
+      "../../lodash/_updateWrapDetails.js": 1104,
+      "../../lodash/_getHolder.js": 1105,
+      "../../lodash/_reorder.js": 1106,
+      "../../lodash/_replaceHolders.js": 1107,
+      "../../lodash/_createPartial.js": 1108,
+      "../../lodash/_mergeData.js": 1109,
+      "../../lodash/curry.js": 1110,
+      "../../lodash/iteratee.js": 1111,
+      "../../lodash/rearg.js": 1112,
+      "../../lodash/_flatRest.js": 1113,
+      "../../lodash/toPath.js": 1114
     }
   },
   "nextFreeChunkId": 5,
diff --git a/package.json b/package.json
index 663bee3737..652217aef1 100644
--- a/package.json
+++ b/package.json
@@ -1,6 +1,6 @@
 {
   "name": "debugger.html",
-  "version": "0.4.0",
+  "version": "0.5.0",
   "license": "MPL-2.0",
   "repository": {
     "url": "git://github.com/devtools-html/debugger.html.git",
diff --git a/src/components/Editor/Editor.css b/src/components/Editor/Editor.css
index d53db79226..3253fa50ff 100644
--- a/src/components/Editor/Editor.css
+++ b/src/components/Editor/Editor.css
@@ -1,6 +1,9 @@
 .editor-wrapper {
   --debug-line-background: rgba(226, 236, 247, 0.5);
   --debug-line-border: rgb(145, 188, 219);
+  --editor-searchbar-height: 27px;
+  --editor-second-searchbar-height: 27px;
+
 }
 
 .theme-dark .editor-wrapper {
@@ -20,10 +23,6 @@
   --theme-conditional-breakpoint-color: #ccd1d5;
 }
 
-.theme-firebug {
-  --theme-conditional-breakpoint-color: #ccd1d5;
-}
-
 .out-of-scope .CodeMirror-line,
 .out-of-scope .CodeMirror-linenumber {
   opacity: 0.8;
diff --git a/src/components/Editor/SearchBar.css b/src/components/Editor/SearchBar.css
index 8619105d5d..f2f60f5698 100644
--- a/src/components/Editor/SearchBar.css
+++ b/src/components/Editor/SearchBar.css
@@ -1,8 +1,6 @@
 .search-bar {
   display: flex;
   flex-direction: column;
-  --editor-searchbar-height: 27px;
-  --editor-second-searchbar-height: 27px;
 }
 
 .search-bar .search-field {
diff --git a/src/components/Editor/Tabs.js b/src/components/Editor/Tabs.js
index 41fda73e17..97a2e6e30e 100644
--- a/src/components/Editor/Tabs.js
+++ b/src/components/Editor/Tabs.js
@@ -46,11 +46,16 @@ function getHiddenTabs(sourceTabs: SourcesList, sourceTabEls) {
     return Math.min(...topOffsets);
   }
 
-  const tabTopOffset = getTopOffset();
-  return sourceTabs.filter((tab, index) => {
+  function hasTopOffset(el) {
     // adding 10px helps account for cases where the tab might be offset by
     // styling such as selected tabs which don't have a border.
-    return sourceTabEls[index].getBoundingClientRect().top > tabTopOffset + 10;
+    const tabTopOffset = getTopOffset();
+    return el.getBoundingClientRect().top > tabTopOffset + 10;
+  }
+
+  return sourceTabs.filter((tab, index) => {
+    const element = sourceTabEls[index];
+    return element && hasTopOffset(element);
   });
 }
 
diff --git a/src/components/Outline.js b/src/components/Outline.js
index cb54ab465e..6233bf2f72 100644
--- a/src/components/Outline.js
+++ b/src/components/Outline.js
@@ -46,7 +46,7 @@ class Outline extends Component {
 
     return dom.li(
       {
-        key: `${name}:${location.start.line}`,
+        key: `${name}:${location.start.line}:${location.start.column}`,
         className: "outline-list__element",
         onClick: () => this.selectItem(location)
       },
diff --git a/src/components/SecondaryPanes/Expressions.js b/src/components/SecondaryPanes/Expressions.js
index f8704f7aee..39e09fddde 100644
--- a/src/components/SecondaryPanes/Expressions.js
+++ b/src/components/SecondaryPanes/Expressions.js
@@ -36,6 +36,13 @@ function getValue(expression) {
     };
   }
 
+  if (value.error) {
+    return {
+      path: value.from,
+      value: value.error
+    };
+  }
+
   if (typeof value.result == "object") {
     return {
       path: value.result.actor,
diff --git a/src/test/mochitest/head.js b/src/test/mochitest/head.js
index 37daa22efb..ce0ee4180a 100644
--- a/src/test/mochitest/head.js
+++ b/src/test/mochitest/head.js
@@ -32,7 +32,7 @@
  * @parent mochitest
  */
 
-// shared-head.js handles
+// shared-head.js handles imports, constants, and utility functions
 Services.scriptloader.loadSubScript(
   "chrome://mochitests/content/browser/devtools/client/framework/test/shared-head.js",
   this