Fixed cannot read properties error when trying to save pachube type publisher

[Patrykb0802]

When trying to create/save a pachube type publisher a problem in the form of a pop-up dialog window saying "Cannot read properties of null (reading 'style')" shows up.

To Reproduce

1. Go to Publishers
2. Select Pachube publisher type
3. Fill up creation form
4. While saving a dialog window should pop up -> error

Expected behavior
No dialog window should show up, saving should happen without any additional windows.

Screenshots

Desktop (please complete the following information):

• OS: Linux Mint
• Browser Chrome 114
• Version 2.7.6.1