BUG/MINOR: debug: Don't dump the lua stack if it is not initialized

When the watchdog is fired because of the lua, the stack of the corresponding
lua context is dumped. But we must be sure the lua context is fully initialized
to do so. If we are blocked on the global lua lock, during the lua context
initialization, the lua stask may be NULL.

This patch should fix the issue #776. It must be backported as far as 2.0.
1 file changed