Address issues reported by phpstan #133

phpstan reports the same warnings with both 8 and 9. They should probably be fixed regardless. The signatures are the same, so I imagine they are compatible.

I'm hesitant to fix these, though, because you're still supporting PHP 7.1, and maintaining compatibility with that is awkward. If yo ever release a new version, I'd recommend rector and updating to only supported versions of php.

Very low priority, I just noticed the new version of that library.

phpstan analyze src
29/29 [▓▓▓▓▓▓▓▓▓▓▓▓▓▓▓▓▓▓▓▓▓▓▓▓▓▓▓▓] 100%

Line Svg/Style.php

89 Method Svg\Style::fromAttributes() should return Svg\Style but return statement is missing.
🪪 return.missing
91 Method Svg\Style::fromAttributes() should return Svg\Style but return statement is missing.
🪪 return.missing

Line Svg/Surface/CPdf.php

1109 Undefined variable: $object
🪪 variable.undefined
1111 Undefined variable: $object
🪪 variable.undefined
3624 Call to vsprintf contains 3 placeholders, 4 values given.
🪪 argument.vsprintf
3663 Call to vsprintf contains 3 placeholders, 4 values given.
🪪 argument.vsprintf

Line Svg/Surface/SurfaceCpdf.php

220 Call to an undefined method Svg\Surface\SurfaceCpdf::_convert_gif_bmp_to_png().
🪪 method.notFound

Originally posted by @tacman in #132 (comment)