The error indicates that the installer can't find your "Documents" folder. During installation the installer asks Windows where your Documents folder is, and Windows returns an empty value which triggers the error.
Have you deleted or moved your Documents folder?
If so, you can try this:
1. Browse the "My Documents" folder in your user profile: C:\Users\<User Name>\My Documents
2. Right click on it and click the Location Tab.
3. Click Restore Default Location.
OR, if your Documents folder is on a network drive, try this: https://support.microsoft.com/en-us/kb/937624