EntityMarking: characters array length is wrong

[joeclarkia]

https://github.com/open-dis/open-dis-javascript/blob/master/src/dis7/EntityMarking.js#L26

The character array length is set to 12, but according to the standard, it should be 11. This is an easy mistake because the total EntityMarking length is 12, but the first byte is a character set byte.

Sidenote: I was interested to submit this, my second issue/codefix for open-dis-javascript. I was a little less excited when I realized that I was the one who introduced this bug -- oops!

[leif81]

Thanks for the report @joeclarkia

Will you be interested in submitting a pull request?

[joeclarkia]

#23

I think that's all that is required to fix this.