Prevent login before extra.js is loaded (#3275)

Disable submit button until extra.js with its crypto functions is
loaded.

app/views/auth/formLogin.phtml

@@ -31,7 +31,7 @@
 		</div>
 
 		<div class="form-group form-group-actions">
-			<button id="loginButton" type="submit" class="btn btn-important">
+			<button id="loginButton" type="submit" class="btn btn-important" disabled="disabled">
 				<?= _t('gen.auth.login') ?>
 			</button>
 		</div>

p/scripts/extra.js

@@ -51,8 +51,10 @@ function init_crypto_form() {
 
 	forgetOpenCategories();
 
+	const submit_button = document.querySelector('button[type="submit"]');
+	submit_button.disabled = false;
+
 	crypto_form.onsubmit = function (e) {
-		const submit_button = this.querySelector('button[type="submit"]');
 		submit_button.disabled = true;
 		let success = false;