Bug fix for stock api
Bug fix for stock api

- If a part had an empty image, the thumbnail was improperly encoded

inventree/InvenTree,SchrodingersGat/InvenTree,inventree/InvenTree,SchrodingersGat/InvenTree,SchrodingersGat/InvenTree,inventree/InvenTree,inventree/InvenTree,SchrodingersGat/InvenTree