Not to clear the sign in when there are errors

[Ana06]

Stop clearing the sign in when there are errors to avoid the users filling the data several times.

When you sign in if you write your email wrong, when you click sign in, both the email and password are deleted and you have to write both things again. So, I think it will be better to keep at least the email (I am hesitant about the password as the user can not see what we really wrote).

[apoorv9990]

PR 24: #24