pygrass: include in command also parameters with value equal 0

git-svn-id: https://svn.osgeo.org/grass/grass/trunk@65630 15284696-431f-4ddb-bdfa-cd5b030d7da7

lib/python/pygrass/modules/interface/module.py

@@ -667,10 +667,10 @@ class Module(object):
         skip = ['stdin', 'stdout', 'stderr']
         args = [self.name, ]
         for key in self.inputs:
-            if key not in skip and self.inputs[key].value:
+            if key not in skip and self.inputs[key].value is not None and self.inputs[key].value != '':
                 args.append(self.inputs[key].get_bash())
         for key in self.outputs:
-            if key not in skip and self.outputs[key].value:
+            if key not in skip and self.outputs[key].value is not None and self.outputs[key].value != '':
                 args.append(self.outputs[key].get_bash())
         for flg in self.flags:
             if self.flags[flg].value: