C2: add assert(false) before malformed control flow bailout

In JDK-8303951, an assert(false, ...) statement was added before compilation bailouts that indicate a product bug, to catch these cases when testing in debug mode.

One missing case of this is found in compile.cpp:

https://github.com/openjdk/jdk/blob/9697e5bf74bc7d7fbdf76eed42b8de3c05d69acc/src/hotspot/share/opto/compile.cpp#L4083

Originally encountered in JDK-8362117, where I thought that was a regression introduced in a later version but actually affects JDK 8 -- but it just silently bailed out.