don't crash if boolean source returns None

diff --git a/lib/python/Components/Converter/ConditionalShowHide.py b/lib/python/Components/Converter/ConditionalShowHide.py
index 8d9baf7d567ca5a149de7c76415588e4fb3ec292..2d4b99a228d0b28744d43e59e9efaae65a203e2e 100644 (file)
--- a/lib/python/Components/Converter/ConditionalShowHide.py
+++ b/lib/python/Components/Converter/ConditionalShowHide.py
@@ -5,10 +5,18 @@ class ConditionalShowHide(Converter, object):
                Converter.__init__(self, type)
                self.invert = type == "Invert"
 
+       def calcVisibility(self):
+               b = self.source.boolean
+               if b is None:
+                       return True
+               b ^= self.invert
+               return b
+
        def changed(self, what):
+               vis = self.calcVisibility()
                for x in self.downstream_elements:
-                       x.visible = self.source.boolean ^ self.invert
+                       x.visible = vis
 
        def connectDownstream(self, downstream):
                Converter.connectDownstream(self, downstream)
-               downstream.visible = self.source.boolean ^ self.invert
+               downstream.visible = self.calcVisibility()