Increase agressiveness of short circuit logic; Just check if the node is slicable

That should also filter out platform, buildVolume and convexHulLNodes

cura/BuildVolume.py

@@ -129,8 +129,8 @@ class BuildVolume(SceneNode):
 
     def _onSceneChanged(self, source):
         if self._global_container_stack:
-            # Just ignore the camera scene updates. The build volume won't change because of it!
+            # Ignore anything that is not something we can slice in the first place!
-            if not isinstance(source, Camera):
+            if source.callDecoration("isSliceable"):
                 self._scene_change_timer.start()
 
     def _onSceneChangeTimerFinished(self):

cura/PlatformPhysics.py

@@ -17,7 +17,6 @@ from cura.Scene import ZOffsetDecorator
 
 import random  # used for list shuffling
 
-
 class PlatformPhysics:
     def __init__(self, controller, volume):
         super().__init__()
@@ -40,8 +39,9 @@ class PlatformPhysics:
         Application.getInstance().getPreferences().addPreference("physics/automatic_drop_down", True)
 
     def _onSceneChanged(self, source):
-        if not source.getMeshData():
+        if not source.callDecoration("isSliceable"):
             return
+
         self._change_timer.start()
 
     def _onChangeTimerFinished(self):

plugins/CuraEngineBackend/CuraEngineBackend.py

@@ -477,7 +477,7 @@ class CuraEngineBackend(QObject, Backend):
     #
     #   \param source The scene node that was changed.
     def _onSceneChanged(self, source: SceneNode) -> None:
-        if not isinstance(source, SceneNode) or isinstance(source, Camera):
+        if not source.callDecoration("isSliceable"):
             return
 
         # This case checks if the source node is a node that contains GCode. In this case the