mmdevapi/tests: make sure return values are used (LLVM/Clang)

[Austin English]

-- 
-Austin
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diff --git a/dlls/mmdevapi/tests/propstore.c b/dlls/mmdevapi/tests/propstore.c
index d0a0c86..a16dee1 100644
--- a/dlls/mmdevapi/tests/propstore.c
+++ b/dlls/mmdevapi/tests/propstore.c
@@ -55,10 +55,12 @@ static void test_propertystore(IPropertyStore *store)
 
     pv.vt = VT_EMPTY;
     hr = IPropertyStore_GetValue(store, (const PROPERTYKEY*)&DEVPKEY_DeviceInterface_Enabled, &pv);
+    ok(hr == S_OK, "Failed with %08x\n", hr);
     ok(pv.vt == VT_EMPTY, "Key should not be found\n");
 
     pv.vt = VT_EMPTY;
     hr = IPropertyStore_GetValue(store, (const PROPERTYKEY*)&DEVPKEY_DeviceInterface_ClassGuid, &pv);
+    ok(hr == S_OK, "Failed with %08x\n", hr);
     ok(pv.vt == VT_EMPTY, "Key should not be found\n");
 }