fix(flomni): use _flomnigui_is_missing guard in show_cameras

Match the deleted-widget detection used by all other flomniGuiTools
methods. The previous _flomnigui_check_attribute_not_exists path relied
on hasattr(self.gui.flomni, "Image"/"Image_0"), which returns stale/
mismatched results when docks are recreated, leaving an empty window
after a user closed the GUI mid sample-transfer. _is_deleted() checks
registry membership and reliably triggers a rebuild.

csaxs_bec/bec_ipython_client/plugins/flomni/gui_tools.py

@@ -90,9 +90,9 @@ class flomniGuiTools:
 
     def flomnigui_show_cameras(self):
         self.flomnigui_show_gui()
-        if self._flomnigui_check_attribute_not_exists(
-            "cam_flomni_gripper"
-        ) or self._flomnigui_check_attribute_not_exists("cam_flomni_overview"):
+        if self._flomnigui_is_missing("camera_gripper_image") or self._flomnigui_is_missing(
+            "camera_overview_image"
+        ):
             self.flomnigui_remove_all_docks()
             self.camera_gripper_image = self.gui.flomni.new("Image")
             if self._flomnicam_check_device_exists(dev.cam_flomni_gripper):