If buildplate has errors, slicing is not possible

CURA-2234

cura/BuildVolume.py

@@ -85,6 +85,8 @@ class BuildVolume(SceneNode):
         ExtruderManager.getInstance().activeExtruderChanged.connect(self._onActiveExtruderStackChanged)
         self._onActiveExtruderStackChanged()
 
+        self._has_errors = False
+
     def setWidth(self, width):
         if width: self._width = width
 
@@ -316,10 +318,13 @@ class BuildVolume(SceneNode):
         if rebuild_me:
             self.rebuild()
 
+    def hasErrors(self):
+        return self._has_errors
+
     def _updateDisallowedAreas(self):
         if not self._global_container_stack:
             return
-
+        self._has_errors = False  # Reset.
         disallowed_areas = copy.deepcopy(
             self._global_container_stack.getProperty("machine_disallowed_areas", "value"))
         areas = []
@@ -424,7 +429,7 @@ class BuildVolume(SceneNode):
             if not collision:
                 areas.append(self._prime_tower_area)
                 self._prime_tower_area = None
-
+        self._has_errors = collision
         self._disallowed_areas = areas
 
     ##  Convenience function to calculate the size of the bed adhesion in directions x, y.

plugins/CuraEngineBackend/StartSliceJob.py

@@ -78,6 +78,10 @@ class StartSliceJob(Job):
             self.setResult(StartJobResult.SettingError)
             return
 
+        if Application.getInstance().getBuildVolume().hasErrors():
+            self.setResult(StartJobResult.SettingError)
+            return
+
         # Don't slice if there is a per object setting with an error value.
         for node in DepthFirstIterator(self._scene.getRoot()):
             if type(node) is not SceneNode or not node.isSelectable():