fix: Request::json() json errors when decoding empty string (#52204)

Author: calebdw

src/Illuminate/Http/Request.php

@@ -405,7 +405,7 @@ public function get(string $key, mixed $default = null): mixed
     public function json($key = null, $default = null)
     {
         if (! isset($this->json)) {
-            $this->json = new InputBag((array) json_decode($this->getContent(), true));
+            $this->json = new InputBag((array) json_decode($this->getContent() ?: '[]', true));
         }
 
         if (is_null($key)) {

tests/Http/HttpRequestTest.php

@@ -1606,4 +1606,14 @@ public function testItCanHaveObjectsInJsonPayload()
 
         $this->assertSame(['name' => 'Laravel'], $request->get('framework'));
     }
+
+    public function testItDoesNotGenerateJsonErrorsForEmptyContent()
+    {
+        // clear any existing errors
+        json_encode(null);
+
+        Request::create('', 'GET')->json();
+
+        $this->assertTrue(json_last_error() === JSON_ERROR_NONE);
+    }
 }