GH-1524: Error handling improvement in SendHandler.

Author: JaroslawLegierski

leshan-server-core/src/main/java/org/eclipse/leshan/server/send/SendHandler.java

@@ -24,6 +24,7 @@
 import org.eclipse.leshan.core.node.TimestampedLwM2mNodes;
 import org.eclipse.leshan.core.peer.LwM2mPeer;
 import org.eclipse.leshan.core.request.SendRequest;
+import org.eclipse.leshan.core.request.exception.InvalidRequestException;
 import org.eclipse.leshan.core.response.SendResponse;
 import org.eclipse.leshan.core.response.SendableResponse;
 import org.eclipse.leshan.server.registration.Registration;
@@ -93,7 +94,9 @@ public void run() {
                     onError(updatedRegistration, String.format("Invalid Send Request, server returns %s %s", //
                             sendResponse.getCode().getName(), //
                             sendResponse.getErrorMessage() != null ? "because" + sendResponse.getErrorMessage() : ""),
-                            null);
+                            new InvalidRequestException(
+                                    sendResponse.getErrorMessage() != null ? sendResponse.getErrorMessage()
+                                            : "unknown reason"));
                 }
             }