Fix a crash on a top-level objc string, patch by Nico Weber


git-svn-id: https://llvm.org/svn/llvm-project/cfe/trunk@45370 91177308-0d34-0410-b5e6-96231b3b80d8
diff --git a/test/Parser/expressions.m b/test/Parser/expressions.m
new file mode 100644
index 0000000..8e314ac
--- /dev/null
+++ b/test/Parser/expressions.m
@@ -0,0 +1,6 @@
+// RUN: clang -parse-noop %s
+
+void test1() {
+  @"s";            // expected-warning {{expression result unused}}
+}
+