PHP Notice: Undefined Index

Undefined index ‘file’ on line 244.
Undefined index ‘line’ on line 245.

log-deprecated-notices.php

The lines in question:

$in_file = $this->strip_abspath( $backtrace[ 4 ]['file'] )
$on_line = $backtrace[ 4 ]['line']

Temporarily muted them like so:

$in_file = ( isset( $backtrace[ 4 ]['file'] ) ? $this->strip_abspath( $backtrace[ 4 ]['file'] ) : false );
$on_line = ( isset( $backtrace[ 4 ]['line'] ) ? $backtrace[ 4 ]['line'] : false );

https://wordpress.org/plugins/log-deprecated-notices/