!fixup zero-initialze local variable

Author: fhahn

llvm/lib/Transforms/Vectorize/LoopVectorizationLegality.cpp

@@ -1665,7 +1665,7 @@ bool LoopVectorizationLegality::isVectorizableEarlyExitLoop() {
 
   // Keep a record of all the exiting blocks.
   SmallVector<const SCEVPredicate *, 4> Predicates;
-  BasicBlock *SingleUncountableExitingBlock;
+  BasicBlock *SingleUncountableExitingBlock = nullptr;
   for (BasicBlock *BB : ExitingBlocks) {
     const SCEV *EC =
         PSE.getSE()->getPredicatedExitCount(TheLoop, BB, &Predicates);