vcl: if the ldp user send buf with 0 len, it will assert failed.
vcl: if the ldp user send buf with 0 len, it will assert failed.

Type: fix

Change-Id: I8ff60cf8726c463491c687e170ad0b1026a1303a
Signed-off-by: jiangxiaoming <3d317dba918afca0df4b7da9cfda2739cf24ee60@outlook.com>

chrisy/vpp,chrisy/vpp,FDio/vpp,chrisy/vpp,chrisy/vpp,vpp-dev/vpp,vpp-dev/vpp,FDio/vpp,chrisy/vpp,chrisy/vpp,FDio/vpp,vpp-dev/vpp,FDio/vpp,vpp-dev/vpp,chrisy/vpp,FDio/vpp,FDio/vpp,vpp-dev/vpp,vpp-dev/vpp,vpp-dev/vpp,FDio/vpp,chrisy/vpp,FDio/vpp