fixed bugs reported by PHPStan

Author: dg

src/Bridges/FormsLatte/FormMacros.php

@@ -25,7 +25,7 @@
  * - {inputError name}
  * - {formContainer name} ... {/formContainer}
  */
-class FormMacros extends MacroSet
+final class FormMacros extends MacroSet
 {
 	public static function install(Latte\Compiler $compiler): void
 	{

src/Forms/Form.php

@@ -623,6 +623,7 @@ public function __toString(): string
 				throw $e;
 			}
 			trigger_error('Exception in ' . __METHOD__ . "(): {$e->getMessage()} in {$e->getFile()}:{$e->getLine()}", E_USER_ERROR);
+			return '';
 		}
 	}