Stacktrace Question - StringIndexOutOfBoundsException

Hi All-

I'm trying to troubleshoot a bug that's been eluding me for a while now. Below is the first few lines of the stacktrace that is returned when it pops up. Does anyone know what "1967" refers to in the second line.

java.lang.StringIndexOutOfBoundsException: String index out of range: -1 at java.lang.String.substring(String.java:1967) at controlP5.ControlFont.calculateHeight(Unknown Source) at controlP5.ControlFont.adjust(Unknown Source) at controlP5.Label$MultilineLabel.draw(Unknown Source)