repair bug at Ctrl+S numeric shortcut

src/asammdf/gui/widgets/numeric.py

@@ -1630,6 +1630,7 @@ def keyPressEvent(self, event):
                 signals = []
                 for index in selected_items:
                     signals.append(self.channels.dataView.backend.signals[index].signal)
+
                 if signals:
                     with mdf_module.MDF() as mdf:
                         groups = {}