Bazel build of ONOS GUI package

Change-Id: Id5f9931c38f82afcdcefc49171dd79f2f5bdad14
diff --git a/utils/osgiwrap/src/main/java/org/onlab/osgiwrap/OSGiWrapper.java b/utils/osgiwrap/src/main/java/org/onlab/osgiwrap/OSGiWrapper.java
index c819ebd..b5669fe 100644
--- a/utils/osgiwrap/src/main/java/org/onlab/osgiwrap/OSGiWrapper.java
+++ b/utils/osgiwrap/src/main/java/org/onlab/osgiwrap/OSGiWrapper.java
@@ -273,8 +273,13 @@
         Jar dot = analyzer.getJar();
 
         log("wab %s", wab);
-        analyzer.setBundleClasspath("WEB-INF/classes," +
-                                    analyzer.getProperty(analyzer.BUNDLE_CLASSPATH));
+
+        String specifiedClasspath = analyzer.getProperty(analyzer.BUNDLE_CLASSPATH);
+        String bundleClasspath = "WEB-INF/classes";
+        if (specifiedClasspath != null) {
+            bundleClasspath += "," + specifiedClasspath;
+        }
+        analyzer.setBundleClasspath(bundleClasspath);
 
         Set<String> paths = new HashSet<>(dot.getResources().keySet());