revset: fix 'remote()' failure when remote repo has more revs than local

current 'remote()' implementation uses 'r' variable, even if it is not
initialized when 'if n in repo' is not true.

this causes unexpected exception.

mercurial/revset.py

@@ -775,8 +775,8 b' def remote(repo, subset, x):'
     n = other.lookup(q)
     if n in repo:
         r = repo[n].rev()
-    if r in subset:
-        return [r]
+        if r in subset:
+            return [r]
     return []
 
 def removes(repo, subset, x):