Check for missing options / databaseURL on emulator start (#1016)

When using firebase emulators Realtime Database throws an error due to app.options not existing.
I've found adding an extra check to the database constructor stops this error, and results in the emulator starting up correctly.

Author: Hoppi164

CHANGELOG.md

@@ -1,2 +1,3 @@
 - Parallelizes network calls that occur when validating authorization for onCall handlers.
 - Adds new regions to V2 API
+- Fixes bug where the emulator crashed when given app without an `options` property.

src/providers/database.ts

@@ -369,7 +369,7 @@ export class DataSnapshot {
     private app?: firebase.app.App,
     instance?: string
   ) {
-    if (app && app.options.databaseURL.startsWith('http:')) {
+    if (app?.options?.databaseURL?.startsWith('http:')) {
       // In this case we're dealing with an emulator
       this.instance = app.options.databaseURL;
     } else if (instance) {