Fixed warning running a command queue without any vertex operations

(cherry picked from commit f8b41919dac0fb95553f910d02faafc6d7205692)

src/render/direct3d/SDL_render_d3d.c

@@ -1108,7 +1108,7 @@ static int D3D_RunCommandQueue(SDL_Renderer *renderer, SDL_RenderCommand *cmd, v
         return -1;
     }
 
-    if (vertices) {
+    if (vertsize > 0) {
         /* upload the new VBO data for this set of commands. */
         vbo = data->vertexBuffers[vboidx];
         if (data->vertexBufferSize[vboidx] < vertsize) {