Bug 1604511 - [2.0] Fix Autofill backend nodes handling. r=geckoview-reviewers,snorp

Differential Revision: https://phabricator.services.mozilla.com/D57631

--HG--
extra : moz-landing-system : lando

mobile/android/modules/geckoview/GeckoViewAutofill.jsm

@@ -45,6 +45,11 @@ class GeckoViewAutofill {
   }
 
   _getInfo(aElement, aParent, aRoot, aUsernameField) {
+    if (!this._autofillInfos) {
+      this._autofillInfos = new WeakMap();
+      this._autofillElements = new Map();
+    }
+
     let info = this._autofillInfos.get(aElement);
     if (info) {
       return info;
@@ -107,7 +112,7 @@ class GeckoViewAutofill {
 
   _updateInfoValues(aElements) {
     if (!this._autofillInfos) {
-      return;
+      return [];
     }
 
     const updated = [];
@@ -156,11 +161,6 @@ class GeckoViewAutofill {
 
     this._autofillTasks.delete(aFormLike.rootElement);
 
-    if (!this._autofillInfos) {
-      this._autofillInfos = new WeakMap();
-      this._autofillElements = new Map();
-    }
-
     const window = aFormLike.rootElement.ownerGlobal;
     // Get password field to get better form data via LoginManagerChild.
     let passwordField;