Fix NPE when looking up package-less classes in the boot registry.

We should never resolve package-less classes in the modules file.

Author: gilles-duboscq

substratevm/src/com.oracle.svm.core/src/com/oracle/svm/core/hub/registry/BootClassRegistry.java

@@ -69,6 +69,9 @@ public synchronized Class<?> doLoadClass(Symbol<Type> type) {
         // Only looking into the jimage for now. There could be appended elements.
         // see GraalServices.getSavedProperty("jdk.boot.class.path.append")
         String pkg = packageFromType(type);
+        if (pkg == null) {
+            return null;
+        }
         try {
             String moduleName = ClassRegistries.getBootModuleForPackage(pkg);
             if (moduleName == null) {