Fixed server Closing on invalid $requestPort (#46726)

On a docker deploy I get a random `Undefined array key` when try to manage the `Closing` server response on a undefined `$requestPort`.

Maybe the problem is `getRequestPortFromLine` parse, but for now maybe the best option is check the `$this->requestsPool[$requestPort]` before continue with the output.

src/Illuminate/Foundation/Console/ServeCommand.php

@@ -251,9 +251,12 @@ protected function handleProcessOutput()
                 $this->requestsPool[$requestPort][1] = trim(explode('[200]: GET', $line)[1]);
             } elseif (str($line)->contains(' Closing')) {
                 $requestPort = $this->getRequestPortFromLine($line);
-                $request = $this->requestsPool[$requestPort];
 
-                [$startDate, $file] = $request;
+                if (empty($this->requestsPool[$requestPort])) {
+                    return;
+                }
+
+                [$startDate, $file] = $this->requestsPool[$requestPort];
 
                 $formattedStartedAt = $startDate->format('Y-m-d H:i:s');