Check before trimming string

[bloombar]

I encountered an error when trimming the string here - .trim() was not defined, meaning the str variable was not a string.

Simply checking for the existence of trim above solved the problem, e.g.

    if (!str || !str.trim) {
      return false
    }

I have not thoroughly tested, and I do not know why str is sometimes not defined correctly in my case... but this looks like an easy added check and may be useful for others.