Fix framebuffer clear for particle collider heightfield.

servers/rendering/renderer_rd/forward_clustered/render_forward_clustered.cpp

@@ -2862,7 +2862,7 @@ void RenderForwardClustered::_render_particle_collider_heightfield(RID p_fb, con
 	{
 		//regular forward for now
 		RenderListParameters render_list_params(render_list[RENDER_LIST_SECONDARY].elements.ptr(), render_list[RENDER_LIST_SECONDARY].element_info.ptr(), render_list[RENDER_LIST_SECONDARY].elements.size(), false, pass_mode, 0, true, false, rp_uniform_set);
-		_render_list_with_draw_list(&render_list_params, p_fb);
+		_render_list_with_draw_list(&render_list_params, p_fb, RD::DRAW_CLEAR_ALL);
 	}
 	RD::get_singleton()->draw_command_end_label();
 }