authPrompt: Don't clear querying service unless querying service fails

At the moment we treat a failure in any service as a signal to stop
tracking users responses to service questions.

This commit makes sure we don't stop waiting for answers if a background
service fails.

Part-of: <https://gitlab.gnome.org/GNOME/gnome-shell/-/merge_requests/1821>

js/gdm/authPrompt.js

@@ -321,8 +321,11 @@ var AuthPrompt = GObject.registerClass({
 
     _onVerificationFailed(userVerifier, serviceName, canRetry) {
         const wasQueryingService = this._queryingService === serviceName;
-        this._queryingService = null;
-        this.clear();
+
+        if (wasQueryingService) {
+            this._queryingService = null;
+            this.clear();
+        }
 
         this.updateSensitivity(canRetry);
         this.setActorInDefaultButtonWell(null);