[binutils-gdb] Return EXT_LANG_BT_ERROR in one more spot in py-framefilter.c

[sergiodj+buildbot at sergiodj dot net]

*** TEST RESULTS FOR COMMIT 1f111921a0f8e3f62a19808349ff9bcbd4e54043 ***

Author: Tom Tromey <tom@tromey.com>
Branch: master
Commit: 1f111921a0f8e3f62a19808349ff9bcbd4e54043

Return EXT_LANG_BT_ERROR in one more spot in py-framefilter.c

While reading py-framefilter.c, I found one spot where an exception
could be caught but then not be turned into EXT_LANG_BT_ERROR.  This
patch fixes this spot.

gdb/ChangeLog
2018-03-26  Tom Tromey  <tom@tromey.com>

	* python/py-framefilter.c (py_print_single_arg): Return
	EXT_LANG_BT_ERROR from catch.