Clean up unused GError in case of catch statement without arguments
Clean up unused GError in case of catch statement without arguments

When catch statement has no arguments, no access to a GError is possible
from Vala source code. Therefore, do not create temporary variable which
is not used. Also, clear error object as it is not passed upwards then.

GNOME/vala,frida/vala,tjol/vala-tjol,frida/vala,severinh/vala,GNOME/vala,tjol/vala-tjol,jessevdk/vala,Distrotech/vala,Distrotech/vala,jessevdk/vala,spidermonkdust/vala,lovebug356/vala,flobrosch/vala-fixes,GNOME/vala,kamanashisroy/aroop,Jc2k/vala,Distrotech/vala,severinh/vala,themiwi/vala,xdave/pvala,flobrosch/vala-fixes,themiwi/vala,severinh/vala,frida/vala,GNOME/vala,Jc2k/vala,rvu95/vala,jessevdk/vala,playya/vala,playya/vala,frida/vala,playya/vala,spidermonkdust/vala,flobrosch/vala-fixes,phako/vala,kamanashisroy/aroop,rvu95/vala,rvu95/vala,tjol/vala-tjol,kamanashisroy/aroop,frida/vala,lovebug356/vala,themiwi/vala,phako/vala,spidermonkdust/vala