Fix NPE occurring when module is there but has no wiring

(cherry picked from commit f5e90d1)

tycho-core/src/main/java/org/eclipse/tycho/core/osgitools/DependencyComputer.java

@@ -164,7 +164,7 @@ public Collection<BundleRevision> getParticipatingModules() {
      * @see #DependencyComputer(ModuleContainer)
      */
     public List<DependencyEntry> computeDependencies(ModuleRevision module) {
-        if (module == null) {
+        if (module == null || module.getWiring() == null) {
             return Collections.emptyList();
         }