Allow an empty input file to be parsed correctly

[myclevorname]

Yes, it uses a goto statement. Even though goto statements are considered harmful, I think it is okay in this situation. This fixes #78.

[tari]

Since the implementation of this is the issue, I think the problem can be fixed more easily by changing this only.

Something like..

unsigned char file_head[3];
read_size = fread(file_head, 1, 3, file);
if (read_size == 3 && memcmp(file_head, utf8_endian_mark, sizeof(file_head)) == 0) {
    // Skip UTF-8 BOM
    size -= sizeof(file_head);
} else {
    // Read data needs to be retained
    rewind(file);
}

[myclevorname]

Thanks, I will incorporate that into a new commit.

[tari]

I'd also recommend adding a test for this, but that might not be easy to do since our tests are set up to have metadata in the input file.