Fix: Python: incorrect assert when reading back framebuffers

Detected when looking into #144887

Pull Request: https://projects.blender.org/blender/blender/pulls/145165

source/blender/python/gpu/gpu_py_framebuffer.cc

@@ -637,7 +637,7 @@ static PyObject *pygpu_framebuffer_read_color(BPyGPUFrameBuffer *self,
     const Py_ssize_t shape[3] = {h, w, channels};
     py_buffer = BPyGPU_Buffer_CreatePyObject(pygpu_dataformat.value_found, shape, 3, nullptr);
     BLI_assert(bpygpu_Buffer_size(py_buffer) ==
-               w * h * channels *
+               size_t(w) * size_t(h) * size_t(channels) *
                    GPU_texture_dataformat_size(eGPUDataFormat(pygpu_dataformat.value_found)));
   }