ignore emtpy locale

If locale is set to emtpy string, to not localize text.  Fixes
display of names in opcua-client-gui.  Regression introduced in
6ce8254

Author: bluhm

opcua/ua/uatypes.py

@@ -554,7 +554,7 @@ def Locale(self, locale):
     def to_string(self):
         if self.Text is None:
             return ""
-        if self.Locale is None:
+        if not self.Locale:
             return self.Text
         return self.__str__()