quartz: Don't fail if the filter CLSID doesn't exist.

dlls/quartz/filtermapper.c

@@ -1523,22 +1523,25 @@ static HRESULT WINAPI FilterMapper_UnregisterFilter(IFilterMapper * iface, CLSID
         strcatW(wszKeyName, wszClsid);
 
         lRet = RegOpenKeyExW(HKEY_CLASSES_ROOT, wszKeyName, 0, KEY_WRITE, &hKey);
+        if (lRet == ERROR_FILE_NOT_FOUND)
+            goto done;
         hr = HRESULT_FROM_WIN32(lRet);
     }
 
     if (SUCCEEDED(hr))
     {
         lRet = RegDeleteValueW(hKey, wszMeritName);
-        if (lRet != ERROR_SUCCESS)
+        if (lRet != ERROR_SUCCESS && lRet != ERROR_FILE_NOT_FOUND)
             hr = HRESULT_FROM_WIN32(lRet);
 
         lRet = RegDeleteTreeW(hKey, wszPins);
-        if (lRet != ERROR_SUCCESS)
+        if (lRet != ERROR_SUCCESS && lRet != ERROR_FILE_NOT_FOUND)
             hr = HRESULT_FROM_WIN32(lRet);
 
         RegCloseKey(hKey);
     }
 
+done:
     CoTaskMemFree(wszClsid);
 
     return hr;

dlls/quartz/tests/filtermapper.c

@@ -297,6 +297,12 @@ static void test_legacy_filter_registration(void)
     ret = RegDeleteKeyW(HKEY_CLASSES_ROOT, key_name);
     ok(!ret, "RegDeleteKeyA failed: %lu\n", ret);
 
+    hr = IFilterMapper_RegisterFilter(mapper, clsid, testfilterW, MERIT_UNLIKELY);
+    ok(hr == S_OK, "RegisterFilter failed: %#x\n", hr);
+
+    hr = IFilterMapper_UnregisterFilter(mapper, clsid);
+    ok(hr == S_OK, "FilterMapper_UnregisterFilter failed with %x\n", hr);
+
     IFilterMapper_Release(mapper);
     IFilterMapper2_Release(mapper2);
 }