[ObjCARC] Convert an if to an early continue. NFC

This reduces nesting and makes the logic slightly easier to follow.

Differential Revision: https://reviews.llvm.org/D46371

git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@331422 91177308-0d34-0410-b5e6-96231b3b80d8
1 file changed