fix: some crashes

music_kraken/objects/collection.py

@@ -60,8 +60,10 @@ class Collection(Generic[T]):
             self._contains_ids.remove(__object.id)
 
         for name, value in self._id_to_index_values[__object.id]:
-            del self._indexed_values[name]
-            del self._indexed_to_objects[value]
+            if name in self._indexed_values:
+                del self._indexed_values[name]
+            if value in self._indexed_to_objects:
+                del self._indexed_to_objects[value]
 
         del self._id_to_index_values[__object.id]
 
@@ -281,7 +283,7 @@ class Collection(Generic[T]):
             yield from c.__iter__(finished_ids=finished_ids)
 
     def __merge__(self, __other: Collection, override: bool = False):
-        self.extend(__other.__iter__())
+        self.extend(__other)
 
     def __getitem__(self, item: int):
         if item < len(self._data):

music_kraken/objects/parents.py

@@ -194,17 +194,23 @@ class OuterProxy:
 
         if a._inner is b._inner:
             return
-
+        
         # switch instances if more efficient
         if len(b._inner._refers_to_instances) > len(a._inner._refers_to_instances):
             a, b = b, a
 
         a._inner.__merge__(b._inner, override=override)
         for collection, child_collection in b._inner._is_collection_child.items():
-            collection.children.remove(child_collection)
+            try:
+                collection.children.remove(child_collection)
+            except ValueError:
+                pass
             
         for collection, parent_collection in b._inner._is_collection_parent.items():
-            collection.parents.remove(parent_collection)
+            try:
+                collection.parents.remove(parent_collection)
+            except ValueError:
+                pass
 
         a._inner._refers_to_instances.update(b._inner._refers_to_instances)