THRIFT-713. java: Java compareTo method throws NPE when any field isn't set.

This patch fixes a somewhat egregious bug in the generated compareTo for non-union structs and avoids possible NPEs.

git-svn-id: https://svn.apache.org/repos/asf/incubator/thrift/trunk@915499 13f79535-47bb-0310-9956-ffa450edef68
diff --git a/lib/java/build.xml b/lib/java/build.xml
index 7b18945..9750963 100644
--- a/lib/java/build.xml
+++ b/lib/java/build.xml
@@ -176,6 +176,8 @@
       classpathref="test.classpath" failonerror="true" />
     <java classname="org.apache.thrift.test.DeepCopyTest"
       classpathref="test.classpath" failonerror="true" />
+    <java classname="org.apache.thrift.test.CompareTest"
+      classpathref="test.classpath" failonerror="true" />
     <java classname="org.apache.thrift.test.MetaDataTest"
       classpathref="test.classpath" failonerror="true" />
     <java classname="org.apache.thrift.test.JavaBeansTest"