Fix echo and bamboozle crash

and fix modify to work a bit better... TODO need actual dependency resolution for spell modification

js/builder/atree.js

@@ -844,19 +844,22 @@ const atree_collect_spells = new (class extends ComputeNode {
                     continue;
                 case 'add_spell_prop': {
                     const { base_spell, target_part = null, cost = 0, behavior = 'merge'} = effect;
-                    const ret_spell = ret_spells.get(base_spell);
-                    // TODO: unjankify this...
-                    if ('cost' in ret_spell) { ret_spell.cost += cost; }
-
-                    if (target_part  === null) {
+                    if (target_part === null) {
                         continue;
                     }
 
+                    if (!ret_spells.has(base_spell)) {
+                        continue;
+                    }
+                    const ret_spell = ret_spells.get(base_spell);
+
                     let found_part = false;
                     for (let part of ret_spell.parts) { // TODO: replace with Map? to avoid this linear search... idk prolly good since its not more verbose to type in json
                         if (part.name !== target_part) {
                             continue;
                         }
+                        // we found the part. merge or modify it!
+                        if ('cost' in ret_spell) { ret_spell.cost += cost; }
 
                         if ('multipliers' in effect) {
                             for (const [idx, v] of effect.multipliers.entries()) {  // python: enumerate()

js/builder/atree_constants.js

@@ -8578,6 +8578,7 @@ const atrees = {
                 {
                     "type": "add_spell_prop",
                     "base_spell": 8,
+                    "behavior": "modify",
                     "target_part": "Slash Damage",
                     "multipliers": [ 690, 0, 0, 110, 0, 0 ]
                 }