Merge pull request #820 from firebase/patch-1

Don't disable email entry if email is nil and new accounts are disabled

Author: morganchen12

EmailAuth/FirebaseEmailAuthUI/FUIPasswordSignInViewController.m

@@ -259,7 +259,7 @@ - (UITableViewCell *)tableView:(UITableView *)tableView
   cell.textField.delegate = self;
   if (indexPath.row == 0) {
     cell.label.text = FUILocalizedString(kStr_Email);
-    cell.textField.enabled = NO;
+    cell.textField.enabled = _email == nil;
     _emailField = cell.textField;
     _emailField.text = _email;
     _emailField.placeholder = FUILocalizedString(kStr_EnterYourEmail);