Nullability check for wchar module.

Bugs: b/245972273
Test: adb shell
Change-Id: I9898a1120c2364e5269633a67bf789a8bb943ba5
diff --git a/tests/wchar_test.cpp b/tests/wchar_test.cpp
index 16d4348..8716810 100644
--- a/tests/wchar_test.cpp
+++ b/tests/wchar_test.cpp
@@ -714,7 +714,8 @@
 #if defined(__BIONIC__)
   wchar_t* p;
   size_t size;
-
+#pragma clang diagnostic push
+#pragma clang diagnostic ignored "-Wnonnull"
   // Invalid buffer.
   errno = 0;
   ASSERT_EQ(nullptr, open_wmemstream(nullptr, &size));
@@ -724,6 +725,7 @@
   errno = 0;
   ASSERT_EQ(nullptr, open_wmemstream(&p, nullptr));
   ASSERT_EQ(EINVAL, errno);
+#pragma clang diagnostic pop
 #else
   GTEST_SKIP() << "This test is bionic-specific";
 #endif