Fix #128945: Crash switching modes after duplicating particle system

The particle system's mirror cache wasn't cleared on the new system,
so it was freed twice when cleaning up all the particle edit mode data.

source/blender/editors/physics/particle_object.cc

@@ -1012,6 +1012,7 @@ static void copy_particle_edit(Depsgraph *depsgraph,
   psys->edit = edit;
 
   edit->pathcache = nullptr;
+  edit->mirror_cache = nullptr;
   BLI_listbase_clear(&edit->pathcachebufs);
 
   edit->emitter_field = nullptr;