fix: Prevent using simplexml_load_file() on missing file #139

Job	Run time
PHP 7.4 \| WP 5.5 \| prefer-stable	4m 5s
PHP 7.4 \| WP 5.5 (MS) \| prefer-stable	3m 54s
PHP 7.4 \| WP latest \| prefer-stable	3m 55s
PHP 7.4 \| WP latest (MS) \| prefer-stable	6m 5s
PHP 7.4 \| WP trunk \| prefer-stable	3m 57s
PHP 8.1 \| WP trunk \| prefer-stable	4m 15s
PHP 8.0 \| WP latest \| prefer-stable	6m 25s
PHP 8.1 \| WP latest \| prefer-stable	6m 1s
PHP 7.4 (Imagick) \| WP latest \| prefer-stable	4m 11s
PHP 7.4 (with coverage) \| WP latest \| prefer-stable	3m 54s
	46m 42s

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