client/search: fix js error when pressing esc key

`this` became inaccessible from hide() when the function was called
from outside.
Note: I don't like the behavior of Escape and Delete, as pressing them
more than once reverses their action.

client/js/controls/auto_complete_control.js

@@ -147,7 +147,9 @@ class AutoCompleteControl {
         let func = null;
         if (this._isVisible) {
             if (key === KEY_ESCAPE) {
-                func = this.hide;
+                func = () => {
+                    this.hide();
+                };
             } else if (key === KEY_TAB && shift) {
                 func = () => {
                     this._selectPrevious();