caps: fix compilation warning
caps: fix compilation warning

GST_STATIC_CAPS is missing initializer for GstMiniObject's n_weak_refs and
weak_refs resulting in compilation warning (llvm-gcc  -Wall)

https://bugzilla.gnome.org/show_bug.cgi?id=664927

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