runDialog: Let history trim input

Checking whether the item is empty is now the history’s job, per the
previous commit. The history also returns the trimmed input for us, so
we can avoid doing that work twice.

Part-of: <https://gitlab.gnome.org/GNOME/gnome-shell/-/merge_requests/1653>

js/ui/runDialog.js

@@ -178,11 +178,9 @@ class RunDialog extends ModalDialog.ModalDialog {
     }
 
     _run(input, inTerminal) {
-        input = input.trim();
+        input = this._history.addItem(input); // trims input
         let command = input;
 
-        if (input)
-            this._history.addItem(input);
         this._commandError = false;
         let f;
         if (this._enableInternalCommands)