examples: fix bogus g_object_unref in helloworld example
examples: fix bogus g_object_unref in helloworld example

GMainLoop is not a GObject.

https://bugzilla.gnome.org/show_bug.cgi?id=424143

Distrotech/gstreamer,surround-io/gstreamer,lovebug356/gstreamer,shelsonjava/gstreamer,drothlis/gstreamer,drothlis/gstreamer,krieger-od/gstreamer,ylatuya/gstreamer,ylatuya/gstreamer,justinjoy/gstreamer,surround-io/gstreamer,mparis/gstreamer,krichter722/gstreamer,lovebug356/gstreamer,jpakkane/gstreamer,jpakkane/gstreamer,jpxiong/gstreamer,lovebug356/gstreamer,krieger-od/gstreamer,cfoch/gstreamer,Lachann/gstreamer,cablelabs/gstreamer,StreamUtils/gstreamer,lubosz/gstreamer,justinjoy/gstreamer,ensonic/gstreamer,Lachann/gstreamer,shelsonjava/gstreamer,StreamUtils/gstreamer,krichter722/gstreamer,ensonic/gstreamer,StreamUtils/gstreamer,mparis/gstreamer,cfoch/gstreamer,justinjoy/gstreamer,krieger-od/gstreamer,collects/gstreamer,surround-io/gstreamer,collects/gstreamer,magcius/gstreamer,jpakkane/gstreamer,StreamUtils/gstreamer,centricular/gstreamer,magcius/gstreamer,cfoch/gstreamer,cfoch/gstreamer,jpakkane/gstreamer,lubosz/gstreamer,ensonic/gstreamer,mparis/gstreamer,surround-io/gstreamer,Distrotech/gstreamer,drothlis/gstreamer,Distrotech/gstreamer,jpxiong/gstreamer,jpxiong/gstreamer,lovebug356/gstreamer,jpxiong/gstreamer,mparis/gstreamer,jpakkane/gstreamer,StreamUtils/gstreamer,cablelabs/gstreamer,collects/gstreamer,Distrotech/gstreamer,shelsonjava/gstreamer,krieger-od/gstreamer,ensonic/gstreamer,mparis/gstreamer,magcius/gstreamer,magcius/gstreamer,ylatuya/gstreamer,krichter722/gstreamer,Lachann/gstreamer,shelsonjava/gstreamer,lubosz/gstreamer,collects/gstreamer,ylatuya/gstreamer,lubosz/gstreamer,magcius/gstreamer,centricular/gstreamer,Lachann/gstreamer,justinjoy/gstreamer,Distrotech/gstreamer,centricular/gstreamer,drothlis/gstreamer,Lachann/gstreamer,centricular/gstreamer,cablelabs/gstreamer,krichter722/gstreamer,centricular/gstreamer,cablelabs/gstreamer,surround-io/gstreamer,lubosz/gstreamer,krichter722/gstreamer,drothlis/gstreamer,collects/gstreamer,cablelabs/gstreamer,krieger-od/gstreamer,shelsonjava/gstreamer,ensonic/gstreamer,jpxiong/gstreamer,justinjoy/gstreamer,cfoch/gstreamer,lovebug356/gstreamer,ylatuya/gstreamer