[dbmanager] Fix emit signal when refresh fields in table

Author: slarosa

python/plugins/db_manager/db_plugins/plugin.py

@@ -1091,7 +1091,7 @@ def rename(self, new_name):
         return self.update(new_name)
 
     def update(self, new_name, new_type_str=None, new_not_null=None, new_default_str=None):
-        self.table().aboutToChange()
+        self.table().aboutToChange.emit()
         if self.name == new_name:
             new_name = None
         if self.type2String() == new_type_str: