In the server mode, when reading from a CLOB or BLOB, if the connection was…

In the server mode, when reading from a CLOB or BLOB, if the connection was closed, a NullPointerException could be thrown instead of an exception saying the connection is closed.

h2/src/main/org/h2/engine/SessionRemote.java

@@ -764,6 +764,7 @@ public class SessionRemote extends SessionWithState implements DataHandler {
     @Override
     public synchronized int readLob(long lobId, byte[] hmac, long offset,
             byte[] buff, int off, int length) {
+        checkClosed();
         for (int i = 0, count = 0; i < transferList.size(); i++) {
             Transfer transfer = transferList.get(i);
             try {