How to reproduce:
1. Open the attached "1300506_Repro" project
2. In the Project window double-click on "New Controls" to open the Input Action window
3. In the Input Action window in the Action Maps section select "New action map"
4. In the Actions section expand the "New action" Action
5. Select "Button With Two Modifiers" and all three "<No Binding>" bindings and delete them (right-click with mouse->Delete)

Expected results: No errors are thrown in the console
Actual results: "Retrieving array element that was out of bounds" and "SerializedProperty m_ActionMaps.Array.data[2].m_Bindings.Array.data[4] has disappeared!" errors are thrown in the Console

Reproducible with: 0.2.10-preview, 1.1.0-preview.2 (2019.4.18f1, 2020.1.17f1, 2020.2.2f1, 2021.1.0b2, 2021.2.0a1)
Not reproducible with: 0.2.1-preview (2018.4.30f1)
Could not test with: 0.1.2-preview, 0.2.8-preview (2019.4.18f1, 2020.1.17f1, 2020.2.2f1, 2021.1.0b2, 2021.2.0a1) because of the CS0234 error

Notes:
- If there are only 2 Bindings in an Action deleting both will produce the error
- On the higher amount of Bindigs it seems that the minimum amount required to delete varies
- With Composite Bindings, it's a bit different:
If the Action contains only a Composite Binding or it's the last Binding then deleting it will not produce the errors but deleting its children Bindings (2 or more) will produce the errors
If there's one basic Binding and one Composite then only deleting the Bindings children (if there are 2 or more) will produce the errors, if Composite is 3rd or later it will produce the error when deleted with another Binding
If the Action contains only multiple Composite Bindings then either deleting two of them or the last Composite's children (2 or more) will produce the errors