Fixed stream_get_meta_data uri is always defined

[yann-eugone]

OK... Now that I fixed PhpStan error in #345

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  Line   Sitemap/DumpingUrlset.php                                             
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  62     Offset 'uri' does not exist on array{timed_out: bool, blocked: bool,  
         eof: bool, unread_bytes: int, stream_type: string, wrapper_type:      
         string, wrapper_data: mixed, mode: string, ...}.                      
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And now that we are running tests on PHP 8.3, we have the opposite error

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  Line   Sitemap/DumpingUrlset.php                                             
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  61     Offset 'uri' on array{timed_out: bool, blocked: bool, eof: bool,      
         unread_bytes: int, stream_type: string, wrapper_type: string,         
         wrapper_data: mixed, mode: string, ...} in isset() always exists and  
         is not nullable.                                                      
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I decided to just ignore this error, because this is no big deal, and it really depends on the PHP version, and we are not even close to only support PHP >= 8.3