Only check executability of a batch when not creating one.

There is no batch yet when creating, so execution is not relevant.

tailbone/views/batch.py

@@ -468,15 +468,17 @@ class BatchCrud(BaseCrud):
         """
         batch = form.fieldset.model
         batch.refreshable = self.refreshable
-        return {
+        kwargs = {
             'batch': batch,
             'batch_display': self.batch_display,
             'batch_display_plural': self.batch_display_plural,
             'execute_title': self.handler.get_execute_title(batch),
-            'execute_enabled': self.executable(batch),
             'route_prefix': self.route_prefix,
             'permission_prefix': self.permission_prefix,
             }
+        if not self.creating:
+            kwargs['execute_enabled'] = self.executable(batch)
+        return kwargs
 
     def executable(self, batch):
         return self.handler.executable(batch)