Fatal error: Uncaught TypeError:

[micinfra1]

I am running cacti 1.2.19 with Xampp 3.3.0 on windows 10. I am trying to capture SNMP - Interface bandwidth on a Cisco Router/Switch but I keep on getting this error.

Sorry, we could not process your last action.
Error: 200 OK
Reason:
Fatal error: Uncaught TypeError: Unsupported operand types: string + int in C:\xampp\htdocs\cacti\lib\rrd.php:937 Stack trace: #0 C:\xampp\htdocs\cacti\lib\graph_variables.php(340): rrdtool_function_fetch(111, 1649417400, 1649473860, 1800) #1 C:\xampp\htdocs\cacti\lib\graph_variables.php(628): bandwidth_summation(111, 1649417400, 1649473860, 6, 300) #2 C:\xampp\htdocs\cacti\lib\rrd.php(1604): variable_bandwidth_summation(Array, Array, Array, Array, 1649417400, 1649473860, 6, 300) #3 C:\xampp\htdocs\cacti\graph_json.php(159): rrdtool_function_graph(97, '0', Array, '', Array, 1) #4 {main} thrown in C:\xampp\htdocs\cacti\lib\rrd.php on line 937