netfilter: nfnetlink_queue: Initialize ctx to avoid memory allocation error

In the Linux kernel, the following vulnerability has been resolved: netfilter: nfnetlink_queue: Initialize ctx to avoid memory allocation error It is possible that ctx in nfqnl_build_packet_message() could be used before it is properly initialize, which is only initialized by nfqnl_get_sk_secctx(). This patch corrects this problem by initializing the lsmctx to a safe value when it is declared. This is similar to the commit 35fcac7a7c25 ("audit: Initialize lsmctx to avoid memory allocation error").