Fix seek after pre-sequence
Fix seek after pre-sequence

Seek handler during ad pre-sequence needs to be unbind if no seek was
performed, otherwise first seek doesn’t work.

tanyaLibatter/mwEmbed,kaltura/mwEmbed,omridevk/mwEmbed,matsuu/mwEmbed,panda-os/mwEmbed,joanpuigsanz/mwEmbed,omridevk/mwEmbed,vladm3/mwEmbed,bordar/mwEmbed,abaylis/mwEmbed,joanpuigsanz/mwEmbed,safarijv/mwEmbed,FlixMaster/mwEmbed,alexmilk/mwEmbed,kaltura/mwEmbed,bordar/mwEmbed,slash851/mwEmbed,panda-os/mwEmbed,panda-os/mwEmbed,FlixMaster/mwEmbed,matsuu/mwEmbed,omridevk/mwEmbed,FlixMaster/mwEmbed,DBezemer/mwEmbed,abaylis/mwEmbed,vladm3/mwEmbed,safarijv/mwEmbed,tanyaLibatter/mwEmbed,DBezemer/mwEmbed,alexmilk/mwEmbed,tanyaLibatter/mwEmbed,DBezemer/mwEmbed,slash851/mwEmbed,joanpuigsanz/mwEmbed,abaylis/mwEmbed,matsuu/mwEmbed,omridevk/mwEmbed,panda-os/mwEmbed,joanpuigsanz/mwEmbed,matsuu/mwEmbed,alexmilk/mwEmbed,kaltura/mwEmbed,DBezemer/mwEmbed,safarijv/mwEmbed,FlixMaster/mwEmbed,slash851/mwEmbed,abaylis/mwEmbed,safarijv/mwEmbed,bordar/mwEmbed,alexmilk/mwEmbed,vladm3/mwEmbed,slash851/mwEmbed,vladm3/mwEmbed,tanyaLibatter/mwEmbed,kaltura/mwEmbed,bordar/mwEmbed