Bug fix to avoid Null Pointer Exception.
diff --git a/src/main/java/net/onrc/onos/graph/GraphDBConnection.java b/src/main/java/net/onrc/onos/graph/GraphDBConnection.java
index f9f3b67..0dfa051 100644
--- a/src/main/java/net/onrc/onos/graph/GraphDBConnection.java
+++ b/src/main/java/net/onrc/onos/graph/GraphDBConnection.java
@@ -125,7 +125,7 @@
 	 * Return whether this connection is valid.
 	 */
 	public Boolean isValid() {
-		return (graph != null || graph.isOpen());
+		return (graph != null && graph.isOpen());
 	}
 
 	/**