Fixed the creation of accounts when using Stellar login
- Added some info messages related to Stellar login
- Added error handling to SqLiteDataProvider::processSql
- Allow account email to be null in the database
When using login with Stellar, the email address remains empty. This was causing issues since the email is also required to be unique, in effect only a single Stellar account could exist.
Resolved this by allowing the email column to be null, since the unique requirement does not cover null values. An empty email will now be stored as null value.
For non-Stellar logins, an email address is still required.