[CYB-217] Fix NullPointerException when running on yarn cluster (#91)

Author: carolynduby

flink-cyber/metron-parser-chain/parser-chains-core/src/main/java/com/cloudera/parserchains/core/DefaultChainBuilder.java

@@ -48,7 +48,9 @@ private ChainLink doBuild(ParserChainSchema chainSchema) throws InvalidParserExc
         for(ParserSchema parserSchema: chainSchema.getParsers()) {
             ChainLink next;
             boolean isRouter = ParserID.router().equals(parserSchema.getId());
-            parserSchema.setBasePath(Paths.get(chainSchema.getBasePath(), "..").toString());
+            if (chainSchema.getBasePath() != null) {
+                parserSchema.setBasePath(Paths.get(chainSchema.getBasePath(), "..").toString());
+            }
             if(isRouter) {
                 next = buildRouter(parserSchema);
             } else {