Add postconditions when exiting from methods returning void
Add postconditions when exiting from methods returning void

rvu95/vala,frida/vala,frida/vala,xdave/pvala,spidermonkdust/vala,flobrosch/vala-fixes,frida/vala,GNOME/vala,frida/vala,rvu95/vala,Distrotech/vala,flobrosch/vala-fixes,GNOME/vala,GNOME/vala,GNOME/vala,spidermonkdust/vala,Distrotech/vala,Distrotech/vala,spidermonkdust/vala,flobrosch/vala-fixes,frida/vala,rvu95/vala