Wildcard callbacks during app initialization behave improperly

Using dash==1.12.0

Looking at the dash-renderer test cbmo003(https://github.com/plotly/dash/blob/dev/tests/integration/callbacks/test_missing_outputs.py#L187), the initialization behavior seems to be incorrect.

The callbacks are:
cb1. items.n_clicks -> (content1.children, content2.children) , children of content1 are of shape {i: number} , children of content2 are of shape {j: number}
cb2. values.n_clicks -> ({i:ALL}.children, {j:ALL}.children)
cb3. ({i:ALL}.children, {j:ALL}.children) -> output.children

At initialization, cb1 and cb3 are triggered

• cb1 returns 2 children from content1 and none for content2, the children of these wildcard components are all null
• cb1 result processing triggers cb2 because there’s now != 0 wildcard outputs
• cb3 is run with children values ([None, None], []) and returns 0because of value or 0
• cb2 is run with None -> ([0, 0], [])

Expected behavior
We trigger cb3 again after assigning the children values after cb2 , similar to the followForward cases. The problem becomes more apparent when changing cb2 to return, for example, 5 instead of 0 on the None case — the test now displays the screenshot below, showing that it never really used the children content to calculate itself during initialization.

Start with the dash-renderer integration test cbmo003 in tests/integration/callbacks/test_missing_outputs.py, especially the linked section around line 187. Trace initialization through cb1, cb2, and cb3 and compare it with the followForward cases. Done means cb3 runs again after wildcard children receive their cb2 values, using those values during initialization.