Fixed null pointer exception. Changed [1] to ['block'] because the re…

…sult of mdToDocument call was a hash and not an array.

src/examples/includes/Include.groovy

@@ -21,7 +21,7 @@ toJSONFilter(CodeBlock) { CodeBlock cb, meta ->
   def result = [cb]
 
   while (result.any {isIncludeBlock(it)}) {
-    result = result.collectMany { isIncludeBlock(it) ? converter.mdToDocument(includeFiles(it.code))[1] : [it] }
+    result = result.collectMany { isIncludeBlock(it) ? converter.mdToDocument(includeFiles(it.code))['blocks'] : [it] }
   }
 
   result