[OpenJDK 2D-Dev] RFR: 8208466: Fix potential memory leak in harfbuzz shaping

[Philip Race]

bug: https://bugs.openjdk.java.net/browse/JDK-8208466
webrev: http://cr.openjdk.java.net/~prr/8208466/

Simple fix for possible memory leaks on error conditions.
This is the same fix as in upstream harfbuzz.

-phil.