After resetting TMP StyleSheet, On creating TMP StyleSheet field "Array element out of bounds" exception is thrown refer to the attached video.

Steps to repro:
1. Create a new project
2. Windows > Package Manager > TextMeshPro Version (3.0.0-preview.14) > Install.
3. Assets > Create >TestMeshPro > Style Sheet > Click on(+) Button
4. Project > TMP_StyleSheet > Inspector > Click on(+) Button > reset
5. Project > TMP_StyleSheet > Inspector > Click on(+) Button

Actual result: TMP StyleSheet field not created and "Array element out of bounds" exception is thrown

Expected result: TMP StyleSheet field gets created and no exception is thrown.

Reproducible in:
2020.2.0a15, 2020.2.0a13 with Version(3.0.0) preview.14 - preview.1

Note: Reset functionality for TextMeshPro Assets is introduced in 2020.2.0a13

Environment:
Windows 10 & macOS 10.14

Stack trace:
Retrieving array element that was out of bounds
UnityEditor.SerializedProperty:InsertArrayElementAtIndex (int)
TMPro.EditorUtilities.TMP_StyleEditor:OnInspectorGUI () (at Library/PackageCache/com.unity.textmeshpro@3.0.0-preview.14/Scripts/Editor/TMP_StyleSheetEditor.cs:210)
UnityEngine.GUIUtility:ProcessEvent (int,intptr,bool&)