bundle2: relax the condition to update transaction.hookargs

This is just a micro optimization. If hookargs is empty, nothing should be
necessary.

mercurial/bundle2.py

@@ -304,7 +304,7 b' class bundleoperation(object):'
     def gettransaction(self):
         transaction = self._gettransaction()
 
-        if self.hookargs is not None:
+        if self.hookargs:
             # the ones added to the transaction supercede those added
             # to the operation.
             self.hookargs.update(transaction.hookargs)