php-svg-lib unsafe attributes merge when parsing `use` tag

php-svg-lib is an SVG file parsing / rendering library. Prior to version 0.5.1, when handling ` tag that references an tag, it merges the attributes from the tag to the tag. The problem pops up especially when the href attribute from the ` tag has not been sanitized. This can lead to an unsafe file read that can cause PHAR Deserialization vulnerability in PHP prior to version 8. Version 0.5.1 contains a patch for this issue.