[Fontconfig] Patch: fix memleak (spotted by Coverity)

[Patrick Lam]

Frederic Crozat wrote:
> Ok, I swear, this is the last fix for today ;)
> 
> This patch fixes a memleak in FcConfigEvaluate with strings (Coverity
> defect #1823).

Got it.

Thanks Dawson (Engler, a cofounder of Coverity.)

pat