prevent exceptions for empty paths

git-svn-id: https://pycam.svn.sourceforge.net/svnroot/pycam/trunk@469 bbaffbd6-741e-11dd-a85d-61de82d9cad9

src/pycam/PathProcessors/ContourCutter.py

@@ -63,6 +63,7 @@ class ContourCutter:
         if paths:
             for p in paths:
                 p.append(p.points[0])
-        self.paths.extend(paths)
+        if paths:
+            self.paths.extend(paths)
         self.pe = None
 

src/pycam/PathProcessors/PolygonCutter.py

@@ -65,5 +65,6 @@ class PolygonCutter:
                     p.append(points[-i-1])
                     p.append(points[i])
                 paths.append(p)
-        self.paths.extend(paths)
+        if paths:
+            self.paths.extend(paths)