controller: Fix error return during processEvents

The return was attempting to return an error from a ctx instead of
the error returned from the previously called function, which results
in a nil pointer dereference.

This was most likely a copy-paste error.

events/controller/controller.go

@@ -289,7 +289,7 @@ func (n *NatsController) processEvents(ctx context.Context) error {
 		if err != nil {
 			eventAcknowleger.nak()
 
-			return errors.Wrap(errProcessEvent, ctx.Err().Error())
+			return errors.Wrap(errProcessEvent, err.Error())
 		}
 
 		// spawn msg process handler