Fields such as 'frame.time_delta' have no byte selection, they are added
with offset 0 and length 0, and evidently 'ws_tvb' is NULL. As
tvb_bytes_to_str expects a non-NULL tvb, explicitly check for this and
add a dummy placeholder. This is intended to be a human-readable string,
so prefer `<EMPTY>` over an empty string.
Change-Id: I32efe4cbefc6bcf0fa9fb94fcf25d7bf1628f3a7
Reviewed-on: https://code.wireshark.org/review/36440
Petri-Dish: Peter Wu <peter@lekensteyn.nl>
Tested-by: Petri Dish Buildbot
Reviewed-by: Peter Wu <peter@lekensteyn.nl>
4a8da5fbde