As you press any of the contacts name under the Chats tab, the app starts to crash. Luckily there is a way to get around this issue.
You should:
Open the BBM app on the home screen
Rather than going to Chats to press a contact name, which crashes the app, tap and hold on a contact till a side bar appears from the right. And at the bottom of the right side of the display, there will be a trash icon, for deleting the whole chat thread. Tap it once to make a pop up display and select End Chat.
Now head over to the Contacts tab, and select the desired contact for the conversation by tapping on any name and start chatting, without the crashing problem.
Note: This is only a temporary solution, but it can work until BlackBerry pushes an update to solve the issue, which is expected to come very soon.
Were you facing the crashing issue? Does this solution help?