little refactoring done

python_app/gui/controllers/app_window_config_mixin.py

@@ -179,12 +179,12 @@ class AppWindowConfigMixin:
             if self._result_history:
                 self._sync_bscan_history_from_results()
             if not self._draw_bscan_heatmap_from_history():
-                self._plot.clear()
+                self._bscan_plot.clear()
             return
         if self._result_history:
             self._draw_results(self._result_history[-1])
             return
-        self._plot.clear()
+        self._bscan_plot.clear()
         self._clear_trace_plots()
 
     def _on_radar_identity_changed(self, *_args) -> None:
@@ -317,6 +317,16 @@ class AppWindowConfigMixin:
 
     def _sync_bscan_frequency_limits_with_radar(self) -> bool:
         """Synchronize B-scan start/stop MHz widget ranges with radar sweep bounds."""
+        required_widgets = (
+            "_start_hz_input",
+            "_stop_hz_input",
+            "_bscan_start_freq_mhz",
+            "_bscan_stop_freq_mhz",
+        )
+        if not all(hasattr(self, widget_name) for widget_name in required_widgets):
+            # Processing callbacks can fire while UI groups are still being built.
+            return False
+
         try:
             radar_start_hz = float(self._start_hz_input.text().strip())
             radar_stop_hz = float(self._stop_hz_input.text().strip())