fix: handle None result in DisplayBuffer

Fix an issue where `result` could be None, causing a crash in
DisplayBuffer. Added a check to ensure `result` is not None before
accessing its values.

xradios/tui/buffers/display.py

@@ -41,7 +41,7 @@ async def run(self):
             except Exception:
                 pass
             else:
-                if all(result.values()):
+                if result and all(result.values()):
                     self.metadata = result
             await asyncio.sleep(30)