System Inotify attempts to call destructed functions

Imported from https://youtrack.roxen.com/issue/PIKE-42

Reported by KG Sterneberg kg@roxen.com

Unknown program: destructed object->function(1,32768,0,"")
pike/lib/modules/System.pmod/_Inotify.so:1: System._Inotify._Instance()->poll()
-:1: Pike.Backend(0)->`()(3600.0)