CBS execs were divided last week on whether to tout signing Bryant Gumbel to a $5 million-a-year deal in on-air promo spots. The promo people were raring to go, seeing in Gumbel a top draw for their warm-and-fuzzy “Welcome home” campaign. They fashioned a spot Thursday from press-conference footage and were itching to air it during the NCAA basketball tournament. But news execs demurred, since his primetime newsmagazine doesn’t air for six more months. They prevailed, but oops! A Gumbel spot aired anyway on CBS’ daytime schedule March 14. A sheepish spokeswoman says the spot aired by mistake and won’t run again.