SDL_gpu.c: Fixed deref-before-check warning

(cherry picked from commit 6a5af95364f7014f99ec6a524e467d3bc5b27aa4)

src/gpu/SDL_gpu.c

@@ -2248,14 +2248,14 @@ void SDL_DrawGPUIndexedPrimitivesIndirect(
 void SDL_EndGPURenderPass(
     SDL_GPURenderPass *render_pass)
 {
-    CommandBufferCommonHeader *commandBufferCommonHeader;
-    commandBufferCommonHeader = (CommandBufferCommonHeader *)RENDERPASS_COMMAND_BUFFER;
-
     if (render_pass == NULL) {
         SDL_InvalidParamError("render_pass");
         return;
     }
 
+    CommandBufferCommonHeader *commandBufferCommonHeader;
+    commandBufferCommonHeader = (CommandBufferCommonHeader *)RENDERPASS_COMMAND_BUFFER;
+
     if (RENDERPASS_DEVICE->debug_mode) {
         CHECK_RENDERPASS
     }