D-Bus: Fix crash when using unsupported types in dynamic clients
D-Bus: Fix crash when using unsupported types in dynamic clients

Fixes bug 586479.

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