Bug - 'btn-cancel-ghost' class duplicates for button in Article Filter dialog

[BuilderNSV]

Environment

• Server OS: Linux
• Browser: Firefox
• Znuny version: 7.1.2

Expected behavior

Only one entry 'btn-cancel-ghost' is present in 'class' attribute for button in Article Filter dialog

Actual behavior

There are 2 entries 'btn-cancel-ghost' in 'class' attribute for button in Article Filter dialog

How to reproduce

Steps to reproduce the behavior:

1. Enable Ticket::Frontend::TicketArticleFilter feature
2. Go to a ticket and call Article Filter dialog (in Article Overview section).
3. Inspect in Firefox HTML code of Reset button and see duplication of 'btn-cancel-ghost' in class parameter:
   <button id="DialogButton1" class="btn-main btn-cancel-ghost btn-cancel-ghost align-left-auto" type="button"><span>Reset</span></button>

Additional information

This happens because of

1. 'btn-cancel-ghost' class added in ArticleFilterEvents() function in Core.Agent.TicketZoom.js at line 401.
2. 'btn-cancel-ghost' class added in TargetNS.ShowDialog function in Core.UI.Dialog.js at line 419.