Please provide a minimal working example that demonstrates the problem in your environment.

If you aren't sure what code is relevant, start with the line number that was reported as having the error. The error message you reported said line 15, but we have no way of knowing what happened before that line.

Many times you will find that when you reduce the script to the smallest segment that still produces the error, the cause of the error becomes obvious.

Note that sometimes the reported line number is misleading, which is often the case when the issue is a missing (or extra) curly bracket, quote, or semi-colon. In those cases you need to iteratively reduce the code until the error no longer occurs, then backstep to see what block contained the error.