The spec doesn't prohibit doing a popFrame in this case. It isn't completely clear how this should work. If a way to make it work cannot be defined and implemented, then the spec should be changed to say this is illegal.
And, in this case, it probably should not return the JVMDI_ERROR_NO_MORE_FRAMES
error but a new error code.

Note that if the thread is waiting on a Thread.sleep() or an Object.wait(),
then a popFrame call returns the JVMDI_ERROR_NO_MORE_FRAMES error because
there are are native methods under these two Java methods. Ideally, popFrames
should be allowed in these cases too.

See test PopFrameAtSyncTest.sh, and bug
    4812902 popFrames hangs if the method is waiting at a synchronize block


###@###.### 2003-03-03
This bug causes these NSK tests to fail:
    nsk/jvmdi/PopFrame/popframe001
    nsk/jvmdi/PopFrame/popframe003
    nsk/jvmdi/PopFrame/popframe005