Clear mini editor base select list cancelled()

Clearing the mini editor when closing is something
all sub-classes were already doing so it makes sense
to pull it up to the base class as the default
cancelled() implementation that can still be overridden
if needed.

src/app/grammar-view.coffee

@@ -35,9 +35,6 @@ class GrammarView extends SelectList
     grammars.unshift(@autoDetect)
     @setArray(grammars)
 
-  cancelled: ->
-    @miniEditor.setText('')
-
   confirmed: (grammar) ->
     @cancel()
     if grammar is @autoDetect

src/app/select-list.coffee

@@ -130,6 +130,9 @@ class SelectList extends View
   restoreFocus: ->
     @previouslyFocusedElement?.focus()
 
+  cancelled: ->
+    @miniEditor.setText('')
+
   cancel: ->
     @list.empty()
     @cancelling = true