onos6307:null pointer dereference in getAvailableBandwidth

Change-Id: Icacb8e4741f3fc02886bcb6383ae4abc423d0ae6
diff --git a/apps/pce/bandwidthmgmt/src/main/java/org/onosproject/bandwidthmgr/BandwidthManager.java b/apps/pce/bandwidthmgmt/src/main/java/org/onosproject/bandwidthmgr/BandwidthManager.java
index e8fc1c7..2c84d7a 100644
--- a/apps/pce/bandwidthmgmt/src/main/java/org/onosproject/bandwidthmgr/BandwidthManager.java
+++ b/apps/pce/bandwidthmgmt/src/main/java/org/onosproject/bandwidthmgr/BandwidthManager.java
@@ -69,7 +69,11 @@
             return unResvBw.iterator().next().doubleValue()
                     - localReservedBw.doubleValue();
         }
-        return unResvBw.iterator().next().doubleValue();
+        if (unResvBw != null) {
+            return unResvBw.iterator().next().doubleValue();
+        } else {
+            return null;
+        }
     }
 
     @Override
@@ -124,4 +128,4 @@
 
         return (bandwidth <= prirZeroBw -  (localAllocBw != null ? localAllocBw : 0));
     }
-}
\ No newline at end of file
+}