Don't segfault when there is no filter arg for a match
Don't segfault when there is no filter arg for a match

Before, running "augtool match '/augeas/files/*/error'" would result in a
segfault. Now it prints all matching entries, regardless of their value.

hercules-team/augeas,dafugg/augeas,kunkku/augeas,dafugg/augeas,mlichvar/augeas,jjlin/augeas,jjlin/augeas,manandbytes/augeas,camptocamp/augeas,mlichvar/augeas,hercules-team/augeas-do-not-use,jjlin/augeas,jtopjian/augeas,domcleal/augeas,camptocamp/augeas,ptoscano/augeas,jasperla/augeas,ptoscano/augeas,kunkku/augeas,camptocamp/augeas,jtopjian/augeas,kumy/augeas,lutter/augeas,mchf/augeas,bkearney/augeas,bkearney/augeas,pevalme/augeas,lutter/augeas,kumy/augeas,raphink/augeas,kumy/augeas,ptoscano/augeas,hercules-team/augeas,bkearney/augeas,mlichvar/augeas,kumy/augeas,mchf/augeas,GeoffWilliams/augeas,MikaelSmith/augeas,domcleal/augeas,jasperla/augeas,dafugg/augeas,domcleal/augeas,camptocamp/augeas,GeoffWilliams/augeas,hercules-team/augeas-do-not-use,MikaelSmith/augeas,bkearney/augeas,pevalme/augeas,pevalme/augeas,lutter/augeas,raphink/augeas,hercules-team/augeas-do-not-use,kunkku/augeas,manandbytes/augeas