multiqueue: Fix tracking of unlinked streams.
multiqueue: Fix tracking of unlinked streams.

33082eb9e42c52e4df848195946f1b7bbce768c5 introduced a bug
preventing sparse unlinked streams from advancing properly,
leading to the queue blocking.

Fixes: #633176

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