Fixed uninitialized memory due to missing returns in canary

Functions which are suppose to crash on non canary builds usually don't return anything which lead to uninitialized memory being used.

src/yuzu/debugger/graphics/graphics_surface.cpp

@@ -30,6 +30,7 @@ static Tegra::Texture::TextureFormat ConvertToTextureFormat(
         return Tegra::Texture::TextureFormat::A2B10G10R10;
     default:
         UNIMPLEMENTED_MSG("Unimplemented RT format");
+        return Tegra::Texture::TextureFormat::A8R8G8B8;
     }
 }