word by word selection selects spaces on wrong end of word and becomes broken

using 344b4ab658a03d81bbdb7bb5f74b2b5c8bd517e8 from main Qt repository on 4.7
branch.

1. use a qml file with a plain TextInput element
2. tap to focus and tap in 'WWW XXX YYY ' - note extra space on the end
3. tap and drag left on the middle 'Y'

note that the selection includes the space on the right of the 'YYY' when it should
not - ie it should be 'YYY' and not 'YYY ' (or sometimes ' YYY ')

4. in some circumstances, selection is non-functional after the above. ie with
' YYY ' all selected, the user is unable to select further words/characters to
the left.

It seems that if you start the selection by clicking on the right side of the middle 'Y' then you get 'YYY ' select, and if you start by clicking on the left side of the middle 'Y', you first get 'YYY' (correct) but then ' YYY ' - in both cases the selection then stops.