i965: Don't bother freeing NULL.
i965: Don't bother freeing NULL.

Commit e16c5c90 was replacing 'region' with 'mt', leaving this
nonsensical code.

Reviewed-by: Jason Ekstrand <b186559eaedf698788888c8a2559b4efb4db10d6@intel.com>

metora/MesaGLSLCompiler,metora/MesaGLSLCompiler,metora/MesaGLSLCompiler