search: Reset the search display when there's no search terms

Destroy the previous search view when there's no search terms, to make
sure old search items don't show up.

js/ui/search.js

@@ -459,6 +459,17 @@ const SearchResults = new Lang.Class({
         }
     },
 
+    _reset: function() {
+        this._terms = [];
+        this._results = {};
+        this._clearDisplay();
+        this._clearSearchTimeout();
+        this._defaultResult = null;
+        this._startingSearch = false;
+
+        this._updateSearchProgress();
+    },
+
     _doSearch: function() {
         this._startingSearch = false;
 
@@ -493,7 +504,7 @@ const SearchResults = new Lang.Class({
         this._cancellable.reset();
 
         if (terms.length == 0) {
-            this._clearSearchTimeout();
+            this._reset();
             return;
         }