[HWAsan] Fix uninitialized variable.

Found by msan.

llvm-svn: 322847
diff --git a/llvm/lib/Transforms/Instrumentation/HWAddressSanitizer.cpp b/llvm/lib/Transforms/Instrumentation/HWAddressSanitizer.cpp
index 15d97b3..df2fe37 100644
--- a/llvm/lib/Transforms/Instrumentation/HWAddressSanitizer.cpp
+++ b/llvm/lib/Transforms/Instrumentation/HWAddressSanitizer.cpp
@@ -186,6 +186,7 @@
   IntptrTy = IRB.getIntPtrTy(DL);
   Int8Ty = IRB.getInt8Ty();
 
+  HwasanCtorFunction = nullptr;
   if (!ClEnableKhwasan) {
     std::tie(HwasanCtorFunction, std::ignore) =
         createSanitizerCtorAndInitFunctions(M, kHwasanModuleCtorName,