[regression] IllegalArgumentException thrown on completionItem/resolve if there's no javadoc

[fbricon]

If a method has no Javadoc, an IllegalArgumentException will be thrown when completing it (completionItem/resolve).

public class Foo {

	public void name() {}
	
	public void bar() {
		nam|  <!-- NPE thrown on completionItem/resolve -->
	}
}

[Error - 9:38:12 PM] Request completionItem/resolve failed.
  Message: Internal error.
  Code: -32603 
java.lang.RuntimeException: java.lang.reflect.InvocationTargetException
	at org.eclipse.lsp4j.jsonrpc.services.GenericEndpoint.lambda$null$0(GenericEndpoint.java:67)
	at org.eclipse.lsp4j.jsonrpc.services.GenericEndpoint.request(GenericEndpoint.java:120)
	at org.eclipse.lsp4j.jsonrpc.RemoteEndpoint.handleRequest(RemoteEndpoint.java:261)
	at org.eclipse.lsp4j.jsonrpc.RemoteEndpoint.consume(RemoteEndpoint.java:190)
	at org.eclipse.jdt.ls.core.internal.ParentProcessWatcher.lambda$0(ParentProcessWatcher.java:121)
	at org.eclipse.lsp4j.jsonrpc.json.StreamMessageProducer.handleMessage(StreamMessageProducer.java:194)
	at org.eclipse.lsp4j.jsonrpc.json.StreamMessageProducer.listen(StreamMessageProducer.java:94)
	at org.eclipse.lsp4j.jsonrpc.json.ConcurrentMessageProcessor.run(ConcurrentMessageProcessor.java:113)
	at java.base/java.util.concurrent.Executors$RunnableAdapter.call(Executors.java:515)
	at java.base/java.util.concurrent.FutureTask.run(FutureTask.java:264)
	at java.base/java.util.concurrent.ThreadPoolExecutor.runWorker(ThreadPoolExecutor.java:1128)
	at java.base/java.util.concurrent.ThreadPoolExecutor$Worker.run(ThreadPoolExecutor.java:628)
	at java.base/java.lang.Thread.run(Thread.java:835)
Caused by: java.lang.reflect.InvocationTargetException
	at java.base/jdk.internal.reflect.NativeMethodAccessorImpl.invoke0(Native Method)
	at java.base/jdk.internal.reflect.NativeMethodAccessorImpl.invoke(NativeMethodAccessorImpl.java:62)
	at java.base/jdk.internal.reflect.DelegatingMethodAccessorImpl.invoke(DelegatingMethodAccessorImpl.java:43)
	at java.base/java.lang.reflect.Method.invoke(Method.java:567)
	at org.eclipse.lsp4j.jsonrpc.services.GenericEndpoint.lambda$null$0(GenericEndpoint.java:65)
	... 12 more
Caused by: java.util.concurrent.CompletionException: java.lang.IllegalArgumentException: Property must not be null: value
	at java.base/java.util.concurrent.CompletableFuture.encodeThrowable(CompletableFuture.java:314)
	at java.base/java.util.concurrent.CompletableFuture.completeThrowable(CompletableFuture.java:319)
	at java.base/java.util.concurrent.CompletableFuture$UniApply.tryFire(CompletableFuture.java:645)
	at java.base/java.util.concurrent.CompletableFuture$Completion.exec(CompletableFuture.java:479)
	at java.base/java.util.concurrent.ForkJoinTask.doExec(ForkJoinTask.java:290)
	at java.base/java.util.concurrent.ForkJoinPool$WorkQueue.topLevelExec(ForkJoinPool.java:1020)
	at java.base/java.util.concurrent.ForkJoinPool.scan(ForkJoinPool.java:1656)
	at java.base/java.util.concurrent.ForkJoinPool.runWorker(ForkJoinPool.java:1594)
	at java.base/java.util.concurrent.ForkJoinWorkerThread.run(ForkJoinWorkerThread.java:177)
Caused by: java.lang.IllegalArgumentException: Property must not be null: value
	at org.eclipse.lsp4j.MarkupContent.setValue(MarkupContent.java:84)
	at org.eclipse.jdt.ls.core.internal.handlers.CompletionResolveHandler.resolve(CompletionResolveHandler.java:178)
	at org.eclipse.jdt.ls.core.internal.handlers.JDTLanguageServer.lambda$5(JDTLanguageServer.java:498)
	at org.eclipse.jdt.ls.core.internal.handlers.JDTLanguageServer.lambda$41(JDTLanguageServer.java:909)
	at java.base/java.util.concurrent.CompletableFuture$UniApply.tryFire(CompletableFuture.java:642)
	... 6 more