lookupMimeType(path, headerBytes) returning TRUE on passing incorrect headerBytes as well

[rastogitech]

Action:

• For a particular file, verify whether the MIME type coming from its extension name and header bytes are both same.
• Task performed: lookupMimeType('file.jpeg', headerBytes: [0x89])

Expected behaviour:
FALSE

Actual result:
TRUE

Description:

• As per the magic_number.dart, the magic bytes of JPEG file is [0xFF, 0xD8].
• So, calling lookupMimeType('file.jpeg', headerBytes: [0x89]) should have returned FALSE, instead of TRUE.
• I'm passing header bytes explicitly, so the match must fail if the header bytes don't match with the magic bytes.