Merge pull request #4461 from matrix-org/t3chguy/register_email_not_possible

If user cannot set email during registration don't tell them to

src/components/views/auth/RegistrationForm.js

@@ -102,11 +102,15 @@ export default createReactClass({
                     "No identity server is configured so you cannot add an email address in order to " +
                     "reset your password in the future.",
                 );
-            } else {
+            } else if (this._showEmail()) {
                 desc = _t(
                     "If you don't specify an email address, you won't be able to reset your password. " +
                     "Are you sure?",
                 );
+            } else {
+                // user can't set an e-mail so don't prompt them to
+                self._doSubmit(ev);
+                return;
             }
 
             const QuestionDialog = sdk.getComponent("dialogs.QuestionDialog");