Open irssi and write "http://google.com" to the input line. Add spaces to the begin of the line as long as there is no space after URL.
PuttyTray will crash with message box saying:
PuTTY Fatal Error:
line==NULL in terminal.c
lineno=5919 y=39 w=128 h=39
FuTTY Develpoment snapshot 2011-04-22:r45 is also affected to this bug.
GH-41: Don't run past the end of the term for urls