serveAssets ignores all assets

[EkkoTheGekko]

Hi John,

Thanks for your reply and solution in issues JohnCoene/packer#23 and #7. I finally had some time again to take a look at it again. The ignoring of the index.js works! However, I noticed that when not adding it to the ignore, it would still be ignored. It turns out that not ignoring any assets results in all assets being ignored. I looked into the problem and found the cause, it has to do with the regular expression that is created find ignored assets. When the vector is empty, the regex becomes "$", this will make it so that all assets are matched and thus ignored. I fixed it like this: ignore_pat <- paste0(c("^", ignore), collapse = "|", sep ="$")

This will always add "^$" to the regular expression which should match nothing and thus ignore nothing.