* in a spreadsheet cell enter =LOG(foobar(SIN(1)))
* invoke Function Wizard on that cell (Ctrl+F2)
  LOG(foobar(SIN(1))) is marked in Formula edit field
* activate Functions page
  LOG(foobar(SIN(1))) is marked in Formula edit field
  Function LOG is selected
* click Next button
  foobar(SIN(1)) is marked in Formula edit field
  Function ABS is selected
* click Next button
  foobar(SIN(1)) is overwritten with ABS( )
* only Cancel solves the problem

foobar() could be any user defined or macro function that have no
function description in the Formula Wizard.

Change-Id: I1cb69a9e38c0b8f251d783bd0f67b4b24ade50d0