PR Python/12212

[Tom Tromey]

>>>>> "Phil" == Phil Muldoon <pmuldoon@redhat.com> writes:

Phil> This patches fixes a case where the API can request the currently
Phil> selected thread from GDB when no inferior is loaded.  This triggers an
Phil> error via assert.  Handle it in Python code instead.

This changes gdb.selected_thread to throw an exception if there is no
thread.  However, this is wrong -- the function is documented to return
None in this case.

Tom