ole32: Add a check for hglobal pointer to GetHGlobalFromStream.

dlls/ole32/hglobalstream.c

@@ -664,10 +664,10 @@ HRESULT WINAPI GetHGlobalFromStream(IStream* pstm, HGLOBAL* phglobal)
 {
   HGLOBALStreamImpl* pStream;
 
-  if (pstm == NULL)
+  if (!pstm || !phglobal)
     return E_INVALIDARG;
 
-  pStream = (HGLOBALStreamImpl*) pstm;
+  pStream = impl_from_IStream(pstm);
 
   /*
    * Verify that the stream object was created with CreateStreamOnHGlobal.

dlls/ole32/tests/hglobalstream.c

@@ -561,6 +561,12 @@ static void test_IStream_Clone(void)
     hr = CreateStreamOnHGlobal(orig_hmem, TRUE, &stream);
     ok(hr == S_OK, "unexpected %#x\n", hr);
 
+    hr = GetHGlobalFromStream(stream, NULL);
+    ok(hr == E_INVALIDARG, "unexpected %#x\n", hr);
+
+    hr = GetHGlobalFromStream(NULL, &hmem);
+    ok(hr == E_INVALIDARG, "unexpected %#x\n", hr);
+
     stream_info(stream, &hmem, &size, &pos);
     ok(hmem == orig_hmem, "handles should match\n");
     ok(size == 0, "unexpected %d\n", size);