In account edit form template, declare new password fields required.

templates/accountform.html

@@ -11,12 +11,12 @@
 		
 		<div>
 			<label for="password">New password</label>
-			<input type="password" id="password" name="new_password" />
+			<input type="password" id="password" name="new_password" required />
 		</div>
 
 		<div>
 			<label for="password2">New password <span>(repeat)</span></label>
-			<input type="password" id="password2" name="new_password2" />
+			<input type="password" id="password2" name="new_password2" required />
 		</div>
 
 		<hr />