Require at least 1 character before _runtime
Require at least 1 character before _runtime

The regex `/_runtime/` will also match strings that start with `_runtime` which means `idx` would be `0` resulting in a bad value from `#{key[0, idx]}`.

This patch makes sure there is at least one character before `_runtime`.  Note that you might also want to put `$` at the end of the regex if you always want `_runtime` to be at the end of the string, else it also matches `_runtimefoobarbaz`
dpogue/rails_server_timings