don't allow keys with empty text to reset the currently selected completion item

forwarding keys with empty text() does not restrict the matching items, but
updating the list of possible completions resets the currently selected item to
the first one

src/plugins/texteditor/completionwidget.cpp

@@ -211,6 +211,9 @@ bool CompletionWidget::event(QEvent *e)
             forwardKeys = false;
             break;
         default:
+            // if a key is forwarded, completion widget is re-opened and selected item is reset to first,
+            // so only forward keys that insert text and refine the completed item
+            forwardKeys = !ke->text().isEmpty();
             break;
         }