ATLAS-1939: added parameter validation to prevent NPE during import

Signed-off-by: Madhan Neethiraj <madhan@apache.org>
diff --git a/webapp/src/main/java/org/apache/atlas/web/resources/AdminResource.java b/webapp/src/main/java/org/apache/atlas/web/resources/AdminResource.java
index 2a5fc90..fe9111b 100755
--- a/webapp/src/main/java/org/apache/atlas/web/resources/AdminResource.java
+++ b/webapp/src/main/java/org/apache/atlas/web/resources/AdminResource.java
@@ -370,6 +370,10 @@
         AtlasImportResult result;
 
         try {
+            if (StringUtils.isEmpty(jsonData)) {
+                jsonData = "{}";
+            }
+
             AtlasImportRequest request = AtlasType.fromJson(jsonData, AtlasImportRequest.class);
             ZipSource zipSource = new ZipSource(inputStream);