Fix uninitialized variable analyzer warning. NFCI.

git-svn-id: https://llvm.org/svn/llvm-project/cfe/trunk@366029 91177308-0d34-0410-b5e6-96231b3b80d8

lib/Sema/SemaDecl.cpp

@@ -12192,7 +12192,7 @@ void Sema::CheckCompleteVariableDeclaration(VarDecl *var) {
 
   // Cache the result of checking for constant initialization.
   Optional<bool> CacheHasConstInit;
-  const Expr *CacheCulprit;
+  const Expr *CacheCulprit = nullptr;
   auto checkConstInit = [&]() mutable {
     if (!CacheHasConstInit)
       CacheHasConstInit = var->getInit()->isConstantInitializer(