ESP8266 stack dumps

[LolLeetx]

my esp8266 keeps crashing and reset,i use exception encoder ,but i dont know how to fix it.Pls help
error code:
Exception (9):
epc1=0x4020b270 epc2=0x00000000 epc3=0x00000000 excvaddr=0x44454c63 depc=0x00000000

stack>>>

ctx: cont
sp: 3ffffc90 end: 3fffffc0 offset: 0190
3ffffe20: 00000000 00000001 3ffffee4 3ffee8e0
3ffffe30: 0000000b 3ffee8a8 3ffef978 402057e0
3ffffe40: 3ffe873b 000001bb 3ffef978 402066a8
3ffffe50: 3ffe87c0 0000003b 3ffef978 40206ad4
3ffffe60: 0000003b 3ffee8a8 0000002e 402034a4
3ffffe70: 3ffffeb8 0000003b 3ffffea0 40207470
3ffffe80: 3ffee8a4 3ffffea0 3ffe87c0 3fffff20
3ffffe90: 3ffee8a4 3ffffee4 3ffef974 40204c53
3ffffea0: 3ffefa0c 003b003f 00fffee4 3ffefc04
3ffffeb0: 003e003f 00ffff90 3ffefadc 0019001f
3ffffec0: 00ffdad0 00000000 3fffff9a 3fffff20
3ffffed0: 3ffee8a4 3ffe876c 3ffef6f4 40202b10
3ffffee0: 3ffefa18 3ffefa98 3ffef734 3ffee97c
3ffffef0: 3fffff90 3fffff20 3ffe8785 40203468
3fffff00: 3fffff28 00000000 3fffff40 3ffee97c
3fffff10: 3fffff90 3ffef6f4 3ffee8a0 40203cc1
3fffff20: 3ffee8e0 3ffef740 61480046 402091b1
3fffff30: 3fffdad0 00000000 3ffee8a0 40203cf9
3fffff40: 4010528d 01726dbe 3ffee9d8 00000000
3fffff50: 0000000a 3ffee9d8 000001f4 3ffee97c
3fffff60: 007a1200 0000000a 3fffff90 40207470
3fffff70: 3fffdad0 3fffff90 3ffe86ac 402074a6
3fffff80: 00000000 00000000 3ffee93c 4020104a
3fffff90: 5f44454c 54415453 8a005355 40100175
3fffffa0: feefeffe 00000000 3ffee93c 402082f0
3fffffb0: feefeffe feefeffe 3ffe857c 40100c5d
<<<stack<<<

my code:
#include <ESP8266WiFi.h>
#include <FirebaseArduino.h>

#define FIREBASE_HOST "xxxxxxxxxxxxxx"
#define FIREBASE_AUTH "xxxxxxxxxxxxx"
#define WIFI_SSID "xxxxxxxxxx"
#define WIFI_PASSWORD "xxxxxxxxxxxxxx#"

void setup() {
Serial.begin(9600);
pinMode(D1, OUTPUT);
// connect to wifi.
WiFi.begin(WIFI_SSID, WIFI_PASSWORD);
Serial.print("connecting");
while (WiFi.status() != WL_CONNECTED) {
Serial.print(".");
delay(500);
}
Serial.println();
Serial.print("connected: ");
Serial.println(WiFi.localIP());
Firebase.begin(FIREBASE_HOST, FIREBASE_AUTH);
Firebase.set("LED_STATUS", 0);
}
int n = 0;
void loop() {
// get value
n = Firebase.getInt("LED_STATUS");
// handle error
if (n==1) {
Serial.println("LED ON");
digitalWrite(D1,HIGH);
delay(500);
return;

}
else {
Serial.println("LED OFF");
digitalWrite(D1,LOW);
delay(500);
return;
}
}

here is the exception encoder: