Path: Fix self.removalshapes declaration [Bug]

Prior to this fix, the `self.removalshapes` variable is not declared if `obj.Base` does not exist, or is empty.  This moves the declaration up in scope to the method level.

src/Mod/Path/PathScripts/PathMillFace.py

@@ -151,13 +151,13 @@ class ObjectFace(PathPocketBase.ObjectPocket):
     def areaOpShapes(self, obj):
         """areaOpShapes(obj) ... return top face"""
         # Facing is done either against base objects
+        self.removalshapes = []
         holeShape = None
 
         PathLog.debug("depthparams: {}".format([i for i in self.depthparams]))
 
         if obj.Base:
             PathLog.debug("obj.Base: {}".format(obj.Base))
-            self.removalshapes = []
             faces = []
             holes = []
             holeEnvs = []