Cause an assertion failure if defaultMarkerLayer is destroyed early
Cause an assertion failure if defaultMarkerLayer is destroyed early

This is to investigate a case where the default marker layer of the
editor is destroyed without the editor itself or its buffer being
destroyed, which is causing `Cannot decorate a destroyed marker`
exceptions.

decaffeinate-examples/atom,liuderchi/atom,Mokolea/atom,Mokolea/atom,stinsonga/atom,PKRoma/atom,atom/atom,xream/atom,CraZySacX/atom,kevinrenaers/atom,stinsonga/atom,ardeshirj/atom,CraZySacX/atom,stinsonga/atom,t9md/atom,FIT-CSE2410-A-Bombs/atom,xream/atom,xream/atom,brettle/atom,andrewleverette/atom,stinsonga/atom,ardeshirj/atom,liuderchi/atom,decaffeinate-examples/atom,andrewleverette/atom,ardeshirj/atom,Arcanemagus/atom,PKRoma/atom,FIT-CSE2410-A-Bombs/atom,sotayamashita/atom,Arcanemagus/atom,CraZySacX/atom,PKRoma/atom,andrewleverette/atom,kevinrenaers/atom,decaffeinate-examples/atom,FIT-CSE2410-A-Bombs/atom,brettle/atom,liuderchi/atom,AlexxNica/atom,decaffeinate-examples/atom,kevinrenaers/atom,sotayamashita/atom,atom/atom,atom/atom,AlexxNica/atom,Mokolea/atom,t9md/atom,Arcanemagus/atom,brettle/atom,AlexxNica/atom,t9md/atom,liuderchi/atom,sotayamashita/atom