gr-confirm-move-dialog: Fix _getProjectBranchesSuggestions

Currently fataling because in construct we call
_getProjectBranchesSuggestions without params and
thus is undefined/false.

We remove the check as it is not needed.

Change-Id: I8d4ead0bf3a8c30d0ecefdc190e4ba4ea7ede29d
(cherry picked from commit 7db9fdcdd7e78140fee2ee3b662d94bddcbbe6a9)
diff --git a/polygerrit-ui/app/elements/change/gr-confirm-move-dialog/gr-confirm-move-dialog.ts b/polygerrit-ui/app/elements/change/gr-confirm-move-dialog/gr-confirm-move-dialog.ts
index e9cf19e..7150ddf 100644
--- a/polygerrit-ui/app/elements/change/gr-confirm-move-dialog/gr-confirm-move-dialog.ts
+++ b/polygerrit-ui/app/elements/change/gr-confirm-move-dialog/gr-confirm-move-dialog.ts
@@ -65,7 +65,7 @@
   project?: RepoName;
 
   @property({type: Object})
-  _query?: (_text?: string) => Promise<AutocompleteSuggestion[]>;
+  _query: (input: string) => Promise<AutocompleteSuggestion[]>;
 
   get keyBindings() {
     return {
@@ -75,7 +75,7 @@
 
   constructor() {
     super();
-    this._query = () => this._getProjectBranchesSuggestions();
+    this._query = (text: string) => this._getProjectBranchesSuggestions(text);
   }
 
   _handleConfirmTap(e: Event) {
@@ -101,10 +101,9 @@
   }
 
   _getProjectBranchesSuggestions(
-    input?: string
+    input: string
   ): Promise<AutocompleteSuggestion[]> {
     if (!this.project) return Promise.reject(new Error('Missing project'));
-    if (!input) return Promise.reject(new Error('Missing input'));
     if (input.startsWith('refs/heads/')) {
       input = input.substring('refs/heads/'.length);
     }
diff --git a/polygerrit-ui/app/elements/change/gr-confirm-move-dialog/gr-confirm-move-dialog_test.js b/polygerrit-ui/app/elements/change/gr-confirm-move-dialog/gr-confirm-move-dialog_test.js
index 43bde75..d51388e 100644
--- a/polygerrit-ui/app/elements/change/gr-confirm-move-dialog/gr-confirm-move-dialog_test.js
+++ b/polygerrit-ui/app/elements/change/gr-confirm-move-dialog/gr-confirm-move-dialog_test.js
@@ -65,5 +65,12 @@
       done();
     });
   });
+
+  test('_getProjectBranchesSuggestions input empty string', done => {
+    element._getProjectBranchesSuggestions('').then(branches => {
+      assert.equal(branches.length, 0);
+      done();
+    });
+  });
 });