Vulkan: Fix EndFrameCapture with null wnd

This ensures that a thumbnail is created using the image from last
presented swapchain.

This swapchain, and the thumbnail still could be null. `CreateRDC` was
incorrectly asserting that the thumbnail contained non-null data. In
fact, `CreateRDC` already behaves correctly in the case of null
thumbnail data, so this assertion is removed.

Change-Id: I5b35463898029b0130fe9d8f39dda30e192deef6

renderdoc/core/core.cpp

@@ -932,8 +932,6 @@ RDCFile *RenderDoc::CreateRDC(RDCDriver driver, uint32_t frameNum, const FramePi
     EncodePixelsPNG(outRaw, outPng);
   }
 
-  RDCASSERT(outPng.pixels != NULL);
-
   ret->SetData(driver, ToStr(driver).c_str(), OSUtility::GetMachineIdent(), &outPng);
 
   FileIO::CreateParentDirectory(m_CurrentLogFile);
@@ -1516,4 +1514,4 @@ TEST_CASE("Check ResourceId tostr", "[tostr]")
   CHECK(ToStr(*u.id) == "ResourceId::1311768465173141112");
 }
 
-#endif
+#endif

renderdoc/driver/vulkan/vk_core.cpp

@@ -1580,7 +1580,7 @@ bool WrappedVulkan::EndFrameCapture(void *dev, void *wnd)
   const uint32_t maxSize = 2048;
   RenderDoc::FramePixels fp;
 
-  if(swap != VK_NULL_HANDLE)
+  if(swaprecord != NULL)
   {
     VkDevice device = GetDev();
     VkCommandBuffer cmd = GetNextCmd();