media: vidtv: initialize local pointers upon transfer of memory ownership

In the Linux kernel, the following vulnerability has been resolved: media: vidtv: initialize local pointers upon transfer of memory ownership vidtv_channel_si_init() creates a temporary list (program, service, event) and ownership of the memory itself is transferred to the PAT/SDT/EIT tables through vidtv_psi_pat_program_assign(), vidtv_psi_sdt_service_assign(), vidtv_psi_eit_event_assign(). The problem here is that the local pointer where the memory ownership transfer was completed is not initialized to NULL. This causes the vidtv_psi_pmt_create_sec_for_each_pat_entry() function to fail, and in the flow that jumps to free_eit, the memory that was freed by vidtv_psi_*_table_destroy() can be accessed again by vidtv_psi_*_event_destroy() due to the uninitialized local pointer, so it is freed once again. Therefore, to prevent use-after-free and double-free vulnerability, local pointers must be initialized to NULL when transferring memory ownership.