fix wrongly identifying a node as non-leaf if it has an empty ideas dict
fix wrongly identifying a node as non-leaf if it has an empty ideas dict

BenGardiner/mindmup-as-attack-trees,BenGardiner/mindmup-as-attack-trees,BenGardiner/mindmup-as-attack-trees,BenGardiner/mindmup-as-attack-trees