"TypeError: t.find(...) is null" error prevents signup when using passwordSignupFields: 'USERNAME_ONLY'

[lestephane]

When the signup form does not contain an email field, as is the case when
passwordSignupFields: 'USERNAME_ONLY', clicking on Signup causes the
signup process to fail with the following error in the console:

"TypeError: t.find(...) is null"

The offending line is the following in accounts-entry.js.

Template.entrySignUp.events({
  'submit #signUp': function(event, t) {
    var email, emailRequired, fields, password, passwordErrors, signupCode, trimInput, username, usernameRequired;
    event.preventDefault();
    username = t.find('input[name="username"]') ? t.find('input[name="username"]').value.toLowerCase() : void 0;
    signupCode = t.find('input[name="signupCode"]') ? t.find('input[name="signupCode"]').value : void 0;
    email = t.find('input[type="email"]').value; <<<<<<<<<<<<<<< HERE
    password = t.find('input[type="password"]').value;
    fields = AccountsEntry.settings.passwordSignupFields;

[ryw]

merged PR - thanks for contribution.