fix exercise not loading when totalattempts is 0
fix exercise not loading when totalattempts is 0

christianmemije/kolibri-exercise-perseus-plugin,66eli77/kolibri-exercise-perseus-plugin,learningequality/kolibri-exercise-perseus-plugin,christianmemije/kolibri-exercise-perseus-plugin,66eli77/kolibri-exercise-perseus-plugin,christianmemije/kolibri-exercise-perseus-plugin,66eli77/kolibri-exercise-perseus-plugin,learningequality/kolibri-exercise-perseus-plugin