Fix Volumetric Fog VoxelGI updates

(cherry picked from commit 89d772a7990f28b4e76610cb87abf2237eef460d)

servers/rendering/renderer_rd/environment/fog.cpp

@@ -931,9 +931,10 @@ void Fog::volumetric_fog_update(const VolumetricFogSettings &p_settings, const P
 			uniforms.push_back(u);
 		}
 
-		if (fog->copy_uniform_set.is_null()) {
-			fog->copy_uniform_set = RD::get_singleton()->uniform_set_create(copy_uniforms, volumetric_fog.process_shader.version_get_shader(volumetric_fog.process_shader_version, VolumetricFogShader::VOLUMETRIC_FOG_PROCESS_SHADER_COPY), 0);
+		if (fog->copy_uniform_set.is_valid() && RD::get_singleton()->uniform_set_is_valid(fog->copy_uniform_set)) {
+			RD::get_singleton()->free(fog->copy_uniform_set);
 		}
+		fog->copy_uniform_set = RD::get_singleton()->uniform_set_create(copy_uniforms, volumetric_fog.process_shader.version_get_shader(volumetric_fog.process_shader_version, VolumetricFogShader::VOLUMETRIC_FOG_PROCESS_SHADER_COPY), 0);
 
 		if (!gi_dependent_sets_valid) {
 			fog->gi_dependent_sets.process_uniform_set = RD::get_singleton()->uniform_set_create(uniforms, volumetric_fog.process_shader.version_get_shader(volumetric_fog.process_shader_version, VolumetricFogShader::VOLUMETRIC_FOG_PROCESS_SHADER_FOG), 0);

servers/rendering/renderer_rd/environment/gi.cpp

@@ -3711,6 +3711,12 @@ void GI::setup_voxel_gi_instances(RenderDataRD *p_render_data, Ref<RenderSceneBu
 			}
 			rbgi->uniform_set[v] = RID();
 		}
+
+		if (p_render_buffers->has_custom_data(RB_SCOPE_FOG)) {
+			// VoxelGI instances have changed, so we need to update volumetric fog.
+			Ref<RendererRD::Fog::VolumetricFog> fog = p_render_buffers->get_custom_data(RB_SCOPE_FOG);
+			fog->sync_gi_dependent_sets_validity(true);
+		}
 	}
 
 	if (p_voxel_gi_instances.size() > 0) {