Fix side effects in assertions
Fix side effects in assertions

Fixes bug 624129.

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