code: protected void throwError(final MessageItem messageItem, final Throwable t, final Object... parameters) {
          if (messageItem.getLevel() == JRLevel.Exception ||
                  messageItem.getLevel() == JRLevel.Error && CoreParameters.DEVELOPER_MODE.get()) {
              throw new CoreRuntimeException(messageItem, t, parameters);
          }
      }
docs: If an error is logged when running in Developer Mode, Throw a Runtime Exception.
  
  When an exception is logged and when an error is logged and we are running in Developer Mode
  
  @param messageItem the message to display for the exception thrown
  @param t the throwable source (could be null)
  @param parameters the message parameters