Fix NullReferenceException when ldobj's target is not a valid reference.
Fix NullReferenceException when ldobj's target is not a valid reference.

acourtney2015/JSIL,sander-git/JSIL,sander-git/JSIL,sq/JSIL,mispy/JSIL,acourtney2015/JSIL,hach-que/JSIL,acourtney2015/JSIL,Trattpingvin/JSIL,iskiselev/JSIL,FUSEEProjectTeam/JSIL,x335/JSIL,dmirmilshteyn/JSIL,hach-que/JSIL,volkd/JSIL,mispy/JSIL,TukekeSoft/JSIL,sander-git/JSIL,iskiselev/JSIL,hach-que/JSIL,volkd/JSIL,Trattpingvin/JSIL,dmirmilshteyn/JSIL,volkd/JSIL,iskiselev/JSIL,iskiselev/JSIL,antiufo/JSIL,antiufo/JSIL,sq/JSIL,x335/JSIL,TukekeSoft/JSIL,hach-que/JSIL,antiufo/JSIL,x335/JSIL,acourtney2015/JSIL,TukekeSoft/JSIL,dmirmilshteyn/JSIL,hach-que/JSIL,sq/JSIL,dmirmilshteyn/JSIL,acourtney2015/JSIL,volkd/JSIL,volkd/JSIL,TukekeSoft/JSIL,FUSEEProjectTeam/JSIL,sander-git/JSIL,x335/JSIL,antiufo/JSIL,mispy/JSIL,sander-git/JSIL,FUSEEProjectTeam/JSIL,sq/JSIL,FUSEEProjectTeam/JSIL,iskiselev/JSIL,FUSEEProjectTeam/JSIL,Trattpingvin/JSIL,Trattpingvin/JSIL,sq/JSIL,mispy/JSIL