Reject invalid match criteria with an error.

Previously, using a command like

  [con_id=foo] kill

would kill the currently focused window because while an error for
not being able to parse the con_id was logged, no further action
was taken, which caused the criterion to be ignored. In this case,
the fallback behavior of using the focused window took over.

For con_id, id and window_type we now reject incorrect values with
an error and abort the command.

fixes #2091

testcases/t/260-invalid-criteria.t

@@ -0,0 +1,27 @@
+#!perl
+# vim:ts=4:sw=4:expandtab
+#
+# Please read the following documents before working on tests:
+# • http://build.i3wm.org/docs/testsuite.html
+#   (or docs/testsuite)
+#
+# • http://build.i3wm.org/docs/lib-i3test.html
+#   (alternatively: perldoc ./testcases/lib/i3test.pm)
+#
+# • http://build.i3wm.org/docs/ipc.html
+#   (or docs/ipc)
+#
+# • http://onyxneon.com/books/modern_perl/modern_perl_a4.pdf
+#   (unless you are already familiar with Perl)
+#
+# Ticket: #2091
+use i3test;
+
+my $ws = fresh_workspace;
+open_window;
+
+my $result = cmd '[con_id=foobar] kill';
+is($result->[0]->{success}, 0, 'command was unsuccessful');
+is($result->[0]->{error}, 'Invalid match: invalid con_id', 'correct error is returned');
+
+done_testing;