[widgets][databaseeditor] Make resistant to "empty" JSON

Empty as in "{}"

beat/editor/widgets/databaseeditor.py

@@ -160,7 +160,7 @@ class DatabaseV1Viewer(QWidget):
     def load(self, json_object):
         self.scroll_widget.clear()
 
-        for protocol in json_object["protocols"]:
+        for protocol in json_object.get("protocols", []):
             protocol_viewer = ProtocolViewer()
             protocol_viewer.load(protocol)
             self.scroll_widget.addWidget(protocol_viewer)