some fixes again

python_app/gui/controllers/app_window_plot/trace_plot_mixin.py

@@ -43,7 +43,9 @@ class AppWindowTracePlotMixin:
                 details=f"{exc}\nExpected format: input:output,input:output",
                 once_key=f"pass_through_combo_filter_invalid_{text}",
             )
-            return set()
+            # Fail open: an unparseable filter is ignored (all traces stay visible),
+            # not turned into an empty allow-set that silently hides every trace.
+            return None
 
     def _configure_pass_through_magnitude_axis(self, plot: pg.PlotWidget) -> None:
         """Apply pass-through magnitude-axis autorange or fixed Y window."""