Avoid wedging VDPAU renderer if mixer creation fails

app/streaming/video/ffmpeg-renderers/vdpau.cpp

@@ -541,11 +541,12 @@ void VDPAURenderer::renderFrame(AVFrame* frame)
     // We need to create the mixer on the fly, because we don't know the dimensions
     // of our video surfaces in advance of decoding. We also need to recreate it when
     // the frame format or size changes.
-    if (hasFrameFormatChanged(frame)) {
-        if (m_VideoMixer != 0) {
+    if (hasFrameFormatChanged(frame) && m_VideoMixer != 0) {
         m_VdpVideoMixerDestroy(m_VideoMixer);
+        m_VideoMixer = 0;
     }
 
+    if (m_VideoMixer == 0) {
         VdpChromaType videoSurfaceChroma;
         uint32_t videoSurfaceWidth, videoSurfaceHeight;
         status = m_VdpVideoSurfaceGetParameters(videoSurface, &videoSurfaceChroma,
@@ -580,6 +581,7 @@ void VDPAURenderer::renderFrame(AVFrame* frame)
             SDL_LogError(SDL_LOG_CATEGORY_APPLICATION,
                          "VdpVideoMixerCreate() failed: %s",
                          m_VdpGetErrorString(status));
+            m_VideoMixer = 0;
             return;
         }
     }