Fix an error where we expect the tagged parameters field to be present even

Fix an error where we expect the tagged parameters field to be present even
though the spec (802.11ad-2012) says they are optional.

Communicated to me by the WiFi Alliance. I have captures. Not sure if I can
share them.

Change-Id: Id5998594214ac4b6a1d3baf3cb2f0d4fe6227b40
Signed-off-by: Richard Sharpe <realrichardsharpe@gmail.com>
Reviewed-on: https://code.wireshark.org/review/9785
Petri-Dish: Alexis La Goutte <alexis.lagoutte@gmail.com>
Tested-by: Petri Dish Buildbot <buildbot-no-reply@wireshark.org>
Reviewed-by: Alexis La Goutte <alexis.lagoutte@gmail.com>