AK+Everywhere: Use Optional for URLParser::parse's base_url parameter

Author: https://github.com/networkException
Commit: 9915fa72fb
Pull-request: https://github.com/SerenityOS/serenity/pull/18287
Reviewed-by: https://github.com/linusg

Tests/AK/TestURL.cpp

@@ -411,7 +411,7 @@ TEST_CASE(complete_file_url_with_base)
 TEST_CASE(empty_url_with_base_url)
 {
     URL base_url { "https://foo.com/"sv };
-    URL parsed_url = URLParser::parse(""sv, &base_url);
+    URL parsed_url = URLParser::parse(""sv, base_url);
     EXPECT_EQ(parsed_url.is_valid(), true);
     EXPECT(base_url.equals(parsed_url));
 }