Loss of trunk's dial patterns on save

Trunks dial patterns does not displayed and deleted upon subsequent save. 

Related to FREEPBX-19658 

Steps for reproduction:

1. Add dial patterns to any trunk. 
2. Submit changes
3. Open again trunk's detail page and check dial patterns - it's empty. (But data still presents in mysql database)
4. Submit changes
5. Dial patterns data in database DELETED.

Affected module versions: 15.0.9.9+ (tested on 15.0.9.12)

https://git.freepbx.org/projects/FREEPBX/repos/core/browse/page.trunks.php?at=refs%2Fheads%2Frelease%2F15.0#444

$dialpattern_array is NULL on moment of this check and it is never populate with real data.

if (is_array($dialpattern_array) && count($dialpattern_array) == 0) { $dialpattern_array = core_trunks_get_dialrules($trunknum); }