This week's book giveaway is in the NodeJS forum. We're giving away four copies of Serverless Applications with Node.js and have Slobodan Stojanovic & Aleksandar Simovic on-line! See this thread for details.
While we do not have the benefit of knowin which code caused this, chances are that you are using a SpannableStringBuilder with a zero length String, and that that is not allowed. What do the javadocs say?