Potential out-of-bounds access in QMainWindowLayout::tabPosition

The enumerator has four valid entries, and the tabPositions array is initialized with 4; however, DockCount is the last entry of the enum, so accessing tabPositions[DockCount] would be out of bounds.

Since toDockPos() might return DockCount (it explicitly does that), the access of the tabPositions array will access element 5 of an array that has only 4 entries.

Reported by coverity with Id 218539: https://scan3.coverity.com/reports.htm#v42553/p10113/fileInstanceId=32993532&defectInstanceId=9019438&mergedDefectId=218539