Very strange error. The error also mentions line 10, where only the final part of the body is added. And the message itself is about being unable to parse 0x61 to utf-8, while that should be simply the lowercase “a” in utf-8… which isn’t present in that line
This makes more sense, as š is the first non-ASCII character of that string, on position 16.
The original encoding is probably UTF-16, as it complains about 0x61, which is part of the UTF-16 encoding of that character: 0x0161 http://graphemica.com/š
though it’s still strange it only mentions 0x61 and crashes on it. I’d expect that it would crash on 0x01, or give some garbled up text like usual.