You have 3 options to disable the interior dome lights when the doors are removed:
1. Remove fuse #4
labeled "door sw defeat" found in the fuse box located behind the glove box. It is the far lower, right fuse. Be advised this will also turns off your "Headlight On" reminder chime, but you can still turn on the dome light with the dimmer control as before.
2. Install/wire-in a switch. This can be purchased as a kit through several Jeep parts vendors or you can piece together your own kit very easily. Here's a thread with a nice write-up including pictures:
Interior Light By-Pass Switch Write-Up
3. Install clips that attach to the door pins (see pic below). These are also available from several Jeep parts vendors for around $10/pair.