More robust extra_ghost_elem handling
More robust extra_ghost_elem handling

If such an element is coarsened away, we can still sanely deal with it
as a subactive element, for a while.

This is a workaround, though; the fix for such cases is for user code
to either switch to ghosting functors or be much more careful about
the interaction between extra_ghost_elem tracking and element
coarsening or deletion.

90jrong/libmesh,dschwen/libmesh,roystgnr/libmesh,svallaghe/libmesh,hrittich/libmesh,dschwen/libmesh,balborian/libmesh,giorgiobornia/libmesh,svallaghe/libmesh,BalticPinguin/libmesh,pbauman/libmesh,svallaghe/libmesh,pbauman/libmesh,libMesh/libmesh,BalticPinguin/libmesh,BalticPinguin/libmesh,jwpeterson/libmesh,pbauman/libmesh,balborian/libmesh,jwpeterson/libmesh,dschwen/libmesh,BalticPinguin/libmesh,dschwen/libmesh,roystgnr/libmesh,capitalaslash/libmesh,giorgiobornia/libmesh,balborian/libmesh,dschwen/libmesh,giorgiobornia/libmesh,hrittich/libmesh,svallaghe/libmesh,libMesh/libmesh,giorgiobornia/libmesh,roystgnr/libmesh,hrittich/libmesh,capitalaslash/libmesh,capitalaslash/libmesh,BalticPinguin/libmesh,hrittich/libmesh,svallaghe/libmesh,90jrong/libmesh,libMesh/libmesh,90jrong/libmesh,pbauman/libmesh,balborian/libmesh,svallaghe/libmesh,giorgiobornia/libmesh,90jrong/libmesh,balborian/libmesh,BalticPinguin/libmesh,capitalaslash/libmesh,balborian/libmesh,jwpeterson/libmesh,pbauman/libmesh,libMesh/libmesh,capitalaslash/libmesh,capitalaslash/libmesh,roystgnr/libmesh,roystgnr/libmesh,BalticPinguin/libmesh,dschwen/libmesh,90jrong/libmesh,libMesh/libmesh,90jrong/libmesh,hrittich/libmesh,90jrong/libmesh,hrittich/libmesh,balborian/libmesh,jwpeterson/libmesh,dschwen/libmesh,libMesh/libmesh,90jrong/libmesh,giorgiobornia/libmesh,hrittich/libmesh,pbauman/libmesh,svallaghe/libmesh,balborian/libmesh,jwpeterson/libmesh,jwpeterson/libmesh,roystgnr/libmesh,90jrong/libmesh,roystgnr/libmesh,pbauman/libmesh,jwpeterson/libmesh,libMesh/libmesh,giorgiobornia/libmesh,svallaghe/libmesh,dschwen/libmesh,giorgiobornia/libmesh,libMesh/libmesh,balborian/libmesh,giorgiobornia/libmesh,jwpeterson/libmesh,hrittich/libmesh,pbauman/libmesh,capitalaslash/libmesh,svallaghe/libmesh,hrittich/libmesh,BalticPinguin/libmesh,roystgnr/libmesh,capitalaslash/libmesh,balborian/libmesh,pbauman/libmesh