User defined fit function box hidden behind scroll bar

[jclarkeSTFC]

Describe the bug

If there is a scroll bar in the fit options, then it's impossible to click the button in the Formula box in order to open the User Function Dialog.

To Reproduce Open the fit toolbar on a plot, size the window vertically such that a scroll bar appears, add a UserFunction, then try and open the User Function Dialog

Expected behavior

Button can be clicked

Screenshots

Platform/Version (please complete the following information):

• OS: macOS
• OS Version: 12.7.5
• Mantid Version 6.10.0rc1, 6.9.1

Additional context

Found during smoke testing.

[jhaigh0]

Possibly mac specific, looks okay on windows