Bug-Unable to add extensions excluded rule less than three characters.

Bug Description:

The file extension of some programs is less than three characters. 【Such as Sqlite3:  *.db】 which cannot be added into the extensions excluded rule.  (*.c *.h)

Reproduction steps

Open OneDrive Setting.

1. OneDrive 设置 (OneDrive Setting)

2. 同步并备份 (Sync & backup)

3. 高级设置 (advanced settings)

4. 排除的文件扩展名(File extensions excluded)

扩展名(extensions)

5. Type in a two-length extensions. E.g. db

Then you can see an Error reprot that Invalid rule: 请输入有效的扩展规则 (Please enter a valid rule)