d3d11: Fixed VB state, avoiding unnecessary recreation (Thanks, Alex!).

Fixes Bugzilla #4779.
diff --git a/src/render/direct3d11/SDL_render_d3d11.c b/src/render/direct3d11/SDL_render_d3d11.c
index ef5db84..d75da71 100644
--- a/src/render/direct3d11/SDL_render_d3d11.c
+++ b/src/render/direct3d11/SDL_render_d3d11.c
@@ -1862,6 +1862,8 @@
             return -1;
         }
 
+        rendererData->vertexBufferSizes[vbidx] = dataSizeInBytes;
+
         ID3D11DeviceContext_IASetVertexBuffers(rendererData->d3dContext,
             0,
             1,