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/model.js

@@ -105,6 +105,13 @@ export default class EditorModel {
 
     reset(serializedParts, caret, inputType) {
         this._parts = serializedParts.map(p => this._partCreator.deserializePart(p));
+        // close auto complete if open
+        // this would happen when clearing the composer after sending
+        // a message with the autocomplete still open
+        if (this._autoComplete) {
+            this._autoComplete = null;
+            this._autoCompletePartIdx = null;
+        }
         this._updateCallback(caret, inputType);
     }