It's National Custom Launcher Update Day! Didn't you know? Hot on the heels of Nova Launcher's recent update, Apex Launcher was also bumped up to v1.3. Only, with that update, the launcher decided to FC every time it was opened. Bummer.
You can't keep a good launcher down, so the Apex team just pushed a point update to the launcher - bringing it to v.1.3.1 - that fixes the FC issue, so it works like a top now.