only capture Enter when autocompletion list has selection

this is the old behaviour and makes sense IMO
also close the auto complete when resetting the composer model,
in case it was still open

src/editor/autocomplete.js

@@ -33,6 +33,10 @@ export default class AutocompleteWrapperModel {
         });
     }
 
+    hasSelection() {
+        return this._getAutocompleterComponent().hasSelection();
+    }
+
     onEnter() {
         this._updateCallback({close: true});
     }
@@ -103,7 +107,7 @@ export default class AutocompleteWrapperModel {
             }
             case "#":
                 return this._partCreator.roomPill(completionId);
-            // also used for emoji completion
+            // used for emoji and command completion replacement
             default:
                 return this._partCreator.plain(text);
         }