swaybar: fail gracefully on tokener creation fail
swaybar: fail gracefully on tokener creation fail

This commit adds missing error-handling to the creation of the tokener
instance. The stack depth parameter is used to initialize an array that
json-c prefaults ahead of time, causing INT_MAX to result in out of
memory errors.

Also drop the depth to 256 to prevent this OOM.

Though this fix is not very satisfactory -- json-c could be made to
not prefault -- it should do for now. At the very least, swaybar will
not crash.

Fixes #6126.

1ace/sway,1ace/sway,1ace/sway