Fix some error handling in the libplacebo renderer

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

@@ -769,6 +769,7 @@ bool PlVkRenderer::populateQueues(int videoFormat)
     vkDeviceContext->nb_comp_queues = m_Vulkan->queue_compute.count;
 
     // Select a video decode queue that is capable of decoding our chosen format
+    vkDeviceContext->queue_family_decode_index = -1;
     for (uint32_t i = 0; i < queueFamilyCount; i++) {
         if (queueFamilies[i].queueFamilyProperties.queueFlags & VK_QUEUE_VIDEO_DECODE_BIT_KHR) {
             if (videoFormat & VIDEO_FORMAT_MASK_H264) {
@@ -897,6 +898,16 @@ void PlVkRenderer::waitToRender()
         return;
     }
 
+    // If a swapchain (re)creation failed, m_Swapchain is NULL. We can't render
+    // or resize it, and a device reset has already been requested, so skip this
+    // frame and let the main thread recreate the renderer.
+    if (m_Swapchain == nullptr) {
+        SDL_Event event;
+        event.type = SDL_RENDER_DEVICE_RESET;
+        SDL_PushEvent(&event);
+        return;
+    }
+
 #ifndef Q_OS_WIN32
     // With libplacebo's Vulkan backend, all swap_buffers does is wait for queued
     // presents to finish. This happens to be exactly what we want to do here, since