GH-1679: Fix NPE with resource delta

Author: BoykoAlex

headless-services/jdt-ls-extension/org.springframework.tooling.jdt.ls.commons/src/org/springframework/tooling/jdt/ls/commons/classpath/ClasspathListenerManager.java

@@ -130,7 +130,7 @@ private boolean isClasspathManifestFileChanged(IJavaProject jp, IJavaElementDelt
 			if (delta.getResourceDeltas() != null && (delta.getFlags() & (IJavaElementDelta.F_CONTENT | IJavaElementDelta.F_CHILDREN)) != 0) {
 				IFile classpathFile = jp.getProject().getFile(IJavaProject.CLASSPATH_FILE_NAME);
 				for (IResourceDelta resourceDelta : delta.getResourceDeltas()) {
-					if (classpathFile.equals(resourceDelta.getResource())) {
+					if (resourceDelta != null && classpathFile.equals(resourceDelta.getResource())) {
 						switch (resourceDelta.getKind()) {
 						case IResourceDelta.ADDED:
 							return true;