R74881 Causes Crash in GDI32_WINETEST:font

With the latest Wine Sync R74881 introduced a new test for GetCharacterPlacementA having a NULL entry for the *lpResults parameter. This causes ReactOS to crash when running the "gdi32:font" test on the test bots. The attached patch adds a test for this value being NULL and exits gracefully now so that this test no longer crashes.