## Problem
I use the MGT React `PeoplePicker` with `selectionMode='multiple'` and pass an array of email addresses as `selectedPeople`. The picker renders with no names or pictures and throws: `TypeError: Cannot use 'in' operator to search for 'groupTypes' in [email]`. Passing Graph IDs instead of emails seems to be the documented usage, but emails should work too. What is wrong?
## Verified fix
The error is not about emails vs IDs - it is a React state timing bug. `selectedPeople` was being populated after the initial render (e.g. via `useState(null)` then `setGraphIds(others)`), so on first render the picker received `null` and crashed when iterating over it. The fix, confirmed by the reporter: make sure the array is set before the picker first renders, so `selectedPeople` never starts as null. Initialize your state with the array (emails or IDs) up front, or do not render the picker until the array is populated.
Source: https://github.com/microsoftgraph/microsoft-graph-toolkit/issues/1644