Copy-paste fix pattern
fn main() {
string name = "ClosedBit"
u256 at = 0
if (at < len(name)) {
println(name[at])
}
}Why it happens
The program tried to read a character outside the string.
How to fix it
Check string length before indexing, or use substring with a validated start and count.
Runtime and Studio now show this kind of page from the error dialog: plain message first, stable code second, original details third.