fix stuck on warp/writing mail (#5299)

src/map/pc.cpp

@@ -5927,6 +5927,7 @@ enum e_setpos pc_setpos(struct map_session_data* sd, unsigned short mapindex, in
 	sd->state.changemap = (sd->mapindex != mapindex);
 	sd->state.warping = 1;
 	sd->state.workinprogress = WIP_DISABLE_NONE;
+	sd->state.mail_writing = false;
 
 	if( sd->state.changemap ) { // Misc map-changing settings
 		int curr_map_instance_id = map_getmapdata(sd->bl.m)->instance_id, new_map_instance_id = (mapdata ? mapdata->instance_id : 0);