What Sitcom was the first Sitcom where one of the main cast actors passed away while the series was still airing?

I don't know. William Frawley last appeared on My Three Sons in early 1965. He died in early 1966, while the show was still running. Does he qualify?

What was the FIRST SITCOM in television history where the actor of the main cast passed away while the show was still producing new episodes?

Was it Joesph Kearns of Dennis the Menace who passed on February 17, 1962 as he was George Wilson and was apart of the main cast.

Hattie McDaniel, the star of Beulah, died in 1952 and was replaced and the show kept airing.