RenderStateCache: handle cache file open failures (#802)

Co-authored-by: Paul Weiß <paul.weiss@malighting.de>

Author: Poohl

Graphics/GraphicsTools/interface/RenderStateCache.hpp

@@ -210,8 +210,10 @@ class RenderDeviceWithCache : public RenderDeviceX<ThrowOnError>
             if (pCacheData)
             {
                 FileWrapper CacheDataFile{FilePath, EFileAccessMode::Overwrite};
-                if (CacheDataFile->Write(pCacheData->GetConstDataPtr(), pCacheData->GetSize()))
+                if (CacheDataFile && CacheDataFile->Write(pCacheData->GetConstDataPtr(), pCacheData->GetSize()))
                     LOG_INFO_MESSAGE("Successfully saved state cache file ", FilePath, " (", FormatMemorySize(pCacheData->GetSize()), ").");
+                else
+                    LOG_ERROR_MESSAGE("Failed to save state cache file ", FilePath, " (", FormatMemorySize(pCacheData->GetSize()), ").");
             }
         }
         else