Added regression test for issues that happened with spectral WCSes when no target is defined
Added regression test for issues that happened with spectral WCSes when no target is defined

lpsinger/astropy,saimn/astropy,mhvk/astropy,mhvk/astropy,astropy/astropy,mhvk/astropy,pllim/astropy,saimn/astropy,pllim/astropy,pllim/astropy,larrybradley/astropy,lpsinger/astropy,StuartLittlefair/astropy,astropy/astropy,StuartLittlefair/astropy,StuartLittlefair/astropy,saimn/astropy,StuartLittlefair/astropy,lpsinger/astropy,astropy/astropy,astropy/astropy,lpsinger/astropy,saimn/astropy,pllim/astropy,larrybradley/astropy,larrybradley/astropy,mhvk/astropy,lpsinger/astropy,larrybradley/astropy,StuartLittlefair/astropy,pllim/astropy,larrybradley/astropy,saimn/astropy,astropy/astropy,mhvk/astropy