fixed #5664 (problem with extent parameter)

git-svn-id: http://sextante.googlecode.com/svn/trunk/soft/bindings/qgis-plugin@206 881b9c09-3ef8-f3c2-ec3d-21d735c97f4d

src/sextante/parameters/ParameterExtent.py

@@ -8,7 +8,7 @@ class ParameterExtent(Parameter):
         self.value = None #The value is a string in the form "xmin, xmax, ymin, y max"
 
     def setValue(self, text):
-        if value is None:
+        if text is None:
             self.value = self.default
             return True
         tokens = text.split(",")