Missing validation on adding special characters only for Emails or User Name

Describe the bug
No 'Validation' message appears when we add only "Arithmetic characters" or Special characters in "User name/Email" field and click on 'check'.
(eg. *-+=^ or #$%@ )

To Reproduce
Steps to reproduce the behavior:
1.Open App on Device
2. Click on "Account" icon
3. Enter User name/Email in "Username or Email" text field.
Note: Password should be only "Arithmetic characters" or Special characters.
(eg. *-+=^ or #$%@ )
4. Click on "Check" button.(at top right corner)

Expected behavior
Validation message should be appear when we click on the "Check" button. it should not allow '' "Arithmetic char" or Special char in "User name/Email" field.

**Screenshots **

• Device: iphone 6 (11.2) , Android s6 (7.0)

Inizia dalla schermata Account e dal campo "Username or Email", quindi segui il flusso del pulsante "Check" sia su iPhone che su Android. Riproduci i casi di input mostrati nell’issue, ad esempio solo *-+=^ o #$%@, e conferma che venga visualizzato un messaggio di convalida e che i valori vengano rifiutati.