Fix userdata not copied when trails started

Author: ueshita

servers/rendering/renderer_rd/shaders/particles.glsl

@@ -292,6 +292,24 @@ void main() {
 			PARTICLE.velocity = particles.data[src_idx].velocity;
 			PARTICLE.flags = PARTICLE_FLAG_TRAILED | ((frame_history.data[0].frame & PARTICLE_FRAME_MASK) << PARTICLE_FRAME_SHIFT); //mark it as trailed, save in which frame it will start
 			PARTICLE.xform = particles.data[src_idx].xform;
+#ifdef USERDATA1_USED
+			PARTICLE.userdata1 = particles.data[src_idx].userdata1;
+#endif
+#ifdef USERDATA2_USED
+			PARTICLE.userdata2 = particles.data[src_idx].userdata2;
+#endif
+#ifdef USERDATA3_USED
+			PARTICLE.userdata3 = particles.data[src_idx].userdata3;
+#endif
+#ifdef USERDATA4_USED
+			PARTICLE.userdata4 = particles.data[src_idx].userdata4;
+#endif
+#ifdef USERDATA5_USED
+			PARTICLE.userdata5 = particles.data[src_idx].userdata5;
+#endif
+#ifdef USERDATA6_USED
+			PARTICLE.userdata6 = particles.data[src_idx].userdata6;
+#endif
 		}
 		if (!bool(particles.data[src_idx].flags & PARTICLE_FLAG_ACTIVE)) {
 			// Disable the entire trail if the parent is no longer active.