[Console] Fixed: Trying to access array offset on value of type int

PHP 7.4 throws an error exception when you are accessing an array offset of a value of type int.
There is an if statement inside the __toString() method of the \Symfony\Component\Console\Input\ArrayInput class that checks the first key of each given parameter to the console command.
It throws an ErrorException with the message: Trying to access array offset on value of type int, because of integer keys of the parameters property of the class.
This modification checks and returns the first key of the parameter if PHP can access to it or, it returns the parameter's key itself.

src/Symfony/Component/Console/Input/ArrayInput.php

@@ -107,7 +107,7 @@ public function __toString()
     {
         $params = [];
         foreach ($this->parameters as $param => $val) {
-            if ($param && '-' === $param[0]) {
+            if ($param && '-' === ($param[0] ?? $param)) {
                 if (\is_array($val)) {
                     foreach ($val as $v) {
                         $params[] = $param.('' != $v ? '='.$this->escapeToken($v) : '');