Fix critical when using binary expression in a generics context
Fix critical when using binary expression in a generics context

Fixes bug 735117

GNOME/vala,rvu95/vala,rvu95/vala,frida/vala,frida/vala,flobrosch/vala-fixes,frida/vala,spidermonkdust/vala,frida/vala,spidermonkdust/vala,flobrosch/vala-fixes,GNOME/vala,spidermonkdust/vala,GNOME/vala,rvu95/vala,frida/vala,flobrosch/vala-fixes,GNOME/vala