Fix BaseImportTestCase on JDK 21+ by ignoring internal modules not on classpath

JDK 21+ exposes internal modules (e.g., jdk.management.agent) that appear as package fragment roots but throw JavaModelException when accessed because they are not on the project's build path. This change explicitly ignores these exceptions to prevent test failures.

Author: vogella

ui/org.eclipse.pde.ui.tests/src/org/eclipse/pde/ui/tests/imports/BaseImportTestCase.java

@@ -34,6 +34,7 @@
 import org.eclipse.core.runtime.IStatus;
 import org.eclipse.core.runtime.Platform;
 import org.eclipse.jdt.core.IClasspathEntry;
+import org.eclipse.jdt.core.IJavaModelStatusConstants;
 import org.eclipse.jdt.core.IJavaProject;
 import org.eclipse.jdt.core.IPackageFragmentRoot;
 import org.eclipse.jdt.core.JavaCore;
@@ -199,7 +200,15 @@ private void verifyProject(IPluginModelBase modelImported, boolean isJava) throw
 
 	private void assertSourceAttached(IJavaProject jProject) throws CoreException {
 		for (IPackageFragmentRoot root : jProject.getPackageFragmentRoots()) {
-			IClasspathEntry entry = root.getRawClasspathEntry();
+			IClasspathEntry entry;
+			try {
+				entry = root.getRawClasspathEntry();
+			} catch (JavaModelException e) {
+				if (e.getStatus().getCode() == IJavaModelStatusConstants.ELEMENT_NOT_ON_CLASSPATH) {
+					continue;
+				}
+				throw e;
+			}
 			if (entry.getEntryKind() == IClasspathEntry.CPE_LIBRARY
 					|| (entry.getEntryKind() == IClasspathEntry.CPE_CONTAINER)
 					&& !entry.getPath().equals(PDECore.REQUIRED_PLUGINS_CONTAINER_PATH)) {