[OPENMP] Fix crash on private variables not used in OpenMP region in templates.

llvm-svn: 233913
diff --git a/clang/lib/Sema/SemaOpenMP.cpp b/clang/lib/Sema/SemaOpenMP.cpp
index 7b44953..9255220 100644
--- a/clang/lib/Sema/SemaOpenMP.cpp
+++ b/clang/lib/Sema/SemaOpenMP.cpp
@@ -1199,7 +1199,7 @@
     if (isOpenMPPrivate(Clause->getClauseKind())) {
       for (auto *VarRef : Clause->children()) {
         if (auto *E = cast_or_null<Expr>(VarRef)) {
-          MarkDeclarationsReferencedInExpr(cast<Expr>(E));
+          MarkDeclarationsReferencedInExpr(E);
         }
       }
     }