isisd: fix assert warning

icc (the Intel C Compiler) "knows" that assert() can be disabled by
setting specific optimisation flags, and therefore emits a warning about
missing a return value after an "always-error" assert.

Workaround by returning a value - this probably needs discussion and a
better fix (for all places where the code needs to abort due to internal
errors).

Signed-off-by: David Lamparter <equinox@opensourcerouting.org>
1 file changed