Line cursor invisible (zero sized) if cell_width is small enough

[paolo-sz]

After fixes for #1157 the line cursor had became invisible (zero sized) if the cell_width is small enough (< 8).
The "offending" line is this one:

mintty/src/wintext.c

Line 4120 in 7c90db2

caret_width *= cell_width / 8;

where, if cell_width is less than 8 then caret_width is multiplied by 0.
Maybe it would be better to ensure a minimum value (eg. 1) in case caret_width is zero at that point.

[mintty]

I actually have the habit to close issues after the next release, but thanks anyway.

[mintty]

Released 3.6.2.