QObject::tr() will assert in debug if the final character is '%'

When attempting to format a string which happens to end in a percentage and contain a plural form I ended up writing a tr() line a bit like this:

    auto str1 = QObject::tr("%n point(s) - %1%", "", 2).arg(QString::number(37.5f));

This worked fine in release, however in debug it asserts in QCoreApplication::replacePercentN() which calls at() beyond the final %. There's nothing about this string which makes that final % ambiguous, and that seems like a trivial indexing error. However if for some reason that input string shouldn't be allowed then the documentation should probably note it.

When the attached program is run we see:

ASSERT: "uint(i) < uint(size())" in file c:\qt\msvc2013\x86_64\5.5.1\qtbase\include\qtcore\../../src/corelib/tools/qstring.h, line 851
Debug Error!

Program: C:\Qt\msvc2013\x86_64\5.5.1\qtbase\lib\Qt5Cored.dll
Module: 5.5.1
File: global\qglobal.cpp
Line: 2966

ASSERT: "uint(i) < uint(size())" in file c:\qt\msvc2013\x86_64\5.5.1\qtbase\include\qtcore\../../src/corelib/tools/qstring.h, line 851

(Press Retry to debug the application)