Qt applications crash when special characters are written into QML text boxes

On OSX 10.10 (Yosemite) pasting the following characters into a QML TextField with the font set to Arial will cause a segmentation fault:
힓あ
(note these characters need to be in NFD to reproduce the issue, this can be achieved by pasting them into a filename on OSX which will convert them to NFD, alternatively use the following UTF-8 string \xE1\x84\x92\xE1\x85\xB5\xE1\x86\xB2\xE3\x81\x82)
The crash seems to be caused by

QFontEngine *actualFontEngine = static_cast<QFontEngineMulti *>(fontEngine)->engine(engineIdx);

returning a null pointer.
Adding

static_cast<QFontEngineMulti *>(fontEngine)->ensureEngineAt(engineIdx);

before this call seems to fix the issue.