Avoid NPE

Author: bbimber

singlecell/api-src/org/labkey/api/singlecell/pipeline/AbstractSingleCellPipelineStep.java

@@ -178,7 +178,7 @@ public boolean requiresHashingOrCiteSeq()
     public static class Markdown
     {
         public List<Chunk> chunks;
-        public Chunk setup;
+        public Chunk setup = null;
         public List<String> headerYml;
 
         public void print(PrintWriter out)
@@ -187,7 +187,10 @@ public void print(PrintWriter out)
             headerYml.forEach(out::println);
             out.println("---");
             out.println("");
-            setup.print(out);
+            if (setup != null)
+            {
+                setup.print(out);
+            }
             chunks.forEach(chunk -> chunk.print(out));
         }