[Bug] stripSequenceSets crashes on funnel nodes with undefined children (v2.9.87)

[elPorcharo]

Version

2.9.87

Context

Funnel builder — saving a sequence that contains a conditional node (funnel_condition) followed by a "Wait for tag" node on one of its branches.

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Description

stripSequenceSets in start.js iterates recursively over funnel sequence nodes. When it encounters a node with action_name === "funnel_condition", it unconditionally accesses t.children.no and t.children.yes without checking whether t.children is defined:

stripSequenceSets: function(t) {
    var e = this;
    return this.each(t, function(t) {
        "send_custom_email" == t.action_name
            ? t = e.stripEmailSequence(t)
            : "funnel_condition" == t.action_name && (
                t.children.no = e.stripSequenceSets(t.children.no),
                t.children.yes = e.stripSequenceSets(t.children.yes)
            )
    }), t
}

Nodes that are not send_custom_email or funnel_condition but appear nested inside a conditional branch (e.g. wait_for_tag) can have children as undefined in their serialized structure. The recursive call passes these nodes back into stripSequenceSets, which on the next iteration attempts to access .no on an undefined children property.

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Error

TypeError: can't access property "no", t.children is undefined
    stripSequenceSets start.js:2

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Steps to Reproduce

1. Create a funnel with a funnel_condition node.
2. On either the Yes or No branch, add a Wait for tag action.
3. Click Save.

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Expected Behavior

The funnel saves without errors.

Actual Behavior

TypeError is thrown in stripSequenceSets and the save fails.

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Workaround

Adding a guard on t.children before accessing its properties resolves the issue:

"funnel_condition" == t.action_name && t.children && (
    t.children.no = e.stripSequenceSets(t.children.no),
    t.children.yes = e.stripSequenceSets(t.children.yes)
)