evr/mixer: Handle uninitialized input case in GetOutputAvailableType().

dlls/evr/mixer.c

@@ -533,7 +533,9 @@ static HRESULT WINAPI video_mixer_transform_GetOutputAvailableType(IMFTransform
 
     EnterCriticalSection(&mixer->cs);
 
-    if (index >= mixer->output.type_count)
+    if (!mixer->inputs[0].media_type)
+        hr = MF_E_TRANSFORM_TYPE_NOT_SET;
+    else if (index >= mixer->output.type_count)
         hr = MF_E_NO_MORE_TYPES;
     else
     {

dlls/evr/tests/evr.c

@@ -835,6 +835,9 @@ static void test_default_mixer_type_negotiation(void)
     hr = IMFTransform_GetInputCurrentType(transform, 0, &media_type);
     ok(hr == MF_E_TRANSFORM_TYPE_NOT_SET, "Unexpected hr %#x.\n", hr);
 
+    hr = IMFTransform_GetOutputAvailableType(transform, 0, 0, &media_type);
+    ok(hr == MF_E_TRANSFORM_TYPE_NOT_SET, "Unexpected hr %#x.\n", hr);
+
     hr = MFCreateMediaType(&media_type);
     ok(hr == S_OK, "Failed to create media type, hr %#x.\n", hr);