Several Fixes

[medienbaecker]

I once again fixed some stuff:

• Safari "Sticky" header position. That was my fault when I updated the style and didn't test it in a -webkit-sticky capable browser
• Reduced the width to create space for more tabs
• An empty, required field in a non active tab will now induce a jump to the relevant tab

• Fields with popups (like the color picker) on the very bottom will no longer be clipped.

Before:

After:

[afbora]

Thanks for great contributes @medienbaecker :+1: