Fixit for 0 -> nullptr may create garbled text like nullptnullptr nullptnullptnullptr

Steps to reproduce:

• Use qtbase/dev at 589a01ff6b1eacf81e74a5fc4801572135214f43
• Open Windows QPA plugin at src\plugins\platforms\windows\windows.pro
• Run analyzer and select all nullptr fixits
• This produces sth like the attached patch (which has text like nullptnullptr or nullptnullptnullptr) in it