Finally had a chance to give this a go, it looks like if I run a stream in from FMLE and then stop it with the Stop button, I get the following message printed to the console, followed crtmpserver terminating:
/opt/crtmpserver/sources/applications/flvplayback/src/rtmpappprotocolhandler.cpp:216 INVOKE: FCUnpublish
/opt/crtmpserver/sources/applications/flvplayback/src/rtmpappprotocolhandler.cpp:130 Stream teststream1 closed.
/opt/crtmpserver/sources/common/src/utils/misc/variant.cpp:591 Cast failed: <STR name="">teststream1</STR>
crtmpserver: /opt/crtmpserver/sources/common/src/utils/misc/variant.cpp:591: Variant::operator uint32_t(): Assertion `false' failed.
For added bonus oddness, if I crash FMLE it doesn't exhibit the same problem. Does this mean anything to you?