keras-maskrcnn: Train fails

...
Epoch 00010: saving model to /var/tmp/bat/snapshots/resnet50_csv_10.h5
1564 instances of class java-classic with average precision: 0.9435
1650 instances of class vogue-menthe with average precision: 0.9563
mAP: 0.9499
Epoch 11/50
10000/10000 [==============================] - 7936s 794ms/step - loss: 0.2792 - regression_loss: 0.1874 - classification_loss: 0.0191 - masks_loss: 0.0727

Epoch 00011: saving model to /var/tmp/bat/snapshots/resnet50_csv_11.h5
Traceback (most recent call last):
  File "/home/michael/keras-maskrcnn/keras_maskrcnn/bin/train.py", line 313, in <module>
    main()
  File "/home/michael/keras-maskrcnn/keras_maskrcnn/bin/train.py", line 309, in main
    max_queue_size=1,
  File "/home/michael/.local/lib/python3.5/site-packages/keras/legacy/interfaces.py", line 91, in wrapper
    return func(*args, **kwargs)
  File "/home/michael/.local/lib/python3.5/site-packages/keras/engine/training.py", line 1418, in fit_generator
    initial_epoch=initial_epoch)
  File "/home/michael/.local/lib/python3.5/site-packages/keras/engine/training_generator.py", line 251, in fit_generator
    callbacks.on_epoch_end(epoch, epoch_logs)
  File "/home/michael/.local/lib/python3.5/site-packages/keras/callbacks.py", line 79, in on_epoch_end
    callback.on_epoch_end(epoch, logs)
  File "/home/michael/.local/lib/python3.5/site-packages/keras_retinanet/callbacks/common.py", line 31, in on_epoch_end
    self.callback.on_epoch_end(epoch, logs=logs)
  File "/home/michael/keras-maskrcnn/keras_maskrcnn/bin/../../keras_maskrcnn/callbacks/eval.py", line 66, in on_epoch_end
    save_path=self.save_path
  File "/home/michael/keras-maskrcnn/keras_maskrcnn/bin/../../keras_maskrcnn/utils/eval.py", line 212, in evaluate
    mask = cv2.resize(mask, (box[2] - box[0], box[3] - box[1]))
cv2.error: OpenCV(3.4.3) /io/opencv/modules/imgproc/src/resize.cpp:4045: error: (-215:Assertion failed) !dsize.empty() || (inv_scale_x > 0 && inv_scale_y > 0) in function 'resize'