Fix particles emitting at old location

(cherry picked from commit 91b7c80d2861666bf2981b90510728f6d3ba1a26)

drivers/gles3/rasterizer_storage_gles3.cpp

@@ -6115,6 +6115,9 @@ void RasterizerStorageGLES3::particles_set_emitting(RID p_particles, bool p_emit
 	Particles *particles = particles_owner.getornull(p_particles);
 	ERR_FAIL_COND(!particles);
 
+	if (p_emitting && !particles->emitting) {
+		particles_request_process(p_particles);
+	}
 	particles->emitting = p_emitting;
 }