[PATCH weston] terminal: Fix segmentation fault when processing DCH ANSI escape code

[aaron at correspondwith.me]

> Since d is not used subsequently in this function, why not combine the
> above two if statements into an and clause.  Then the patch is just a
> one-liner.
It needs to short-circuit the else block, so I can't put the conditions
together.

> It looks like this also gets called for ICH codes, where it looks like d
> isn't restricted to positive only values (afaict).  Will this cause any
> weird behaviors in that case?
I'll take a look at the way ICH needs to use it, good catch. :)