Fix member function call on null pointer in Sema::FindInstantiatedDecl.

This bug was reported by UBSan.

llvm-svn: 217059
diff --git a/clang/lib/Sema/SemaTemplateInstantiateDecl.cpp b/clang/lib/Sema/SemaTemplateInstantiateDecl.cpp
index e9d95f2..ce18f6e 100644
--- a/clang/lib/Sema/SemaTemplateInstantiateDecl.cpp
+++ b/clang/lib/Sema/SemaTemplateInstantiateDecl.cpp
@@ -4400,17 +4400,17 @@
       (isa<CXXRecordDecl>(D) && cast<CXXRecordDecl>(D)->isLambda())) {
     // D is a local of some kind. Look into the map of local
     // declarations to their instantiations.
-    typedef LocalInstantiationScope::DeclArgumentPack DeclArgumentPack;
-    llvm::PointerUnion<Decl *, DeclArgumentPack *> *Found
-      = CurrentInstantiationScope->findInstantiationOf(D);
+    if (CurrentInstantiationScope) {
+      if (auto Found = CurrentInstantiationScope->findInstantiationOf(D)) {
+        if (Decl *FD = Found->dyn_cast<Decl *>())
+          return cast<NamedDecl>(FD);
 
-    if (Found) {
-      if (Decl *FD = Found->dyn_cast<Decl *>())
-        return cast<NamedDecl>(FD);
-
-      int PackIdx = ArgumentPackSubstitutionIndex;
-      assert(PackIdx != -1 && "found declaration pack but not pack expanding");
-      return cast<NamedDecl>((*Found->get<DeclArgumentPack *>())[PackIdx]);
+        int PackIdx = ArgumentPackSubstitutionIndex;
+        assert(PackIdx != -1 &&
+               "found declaration pack but not pack expanding");
+        typedef LocalInstantiationScope::DeclArgumentPack DeclArgumentPack;
+        return cast<NamedDecl>((*Found->get<DeclArgumentPack *>())[PackIdx]);
+      }
     }
 
     // If we're performing a partial substitution during template argument