Selecting any entry in navbar apps menu throwns an unknown function error

e.g. /apps/app=apache

(unknown function) called at [/opt/observium/html/includes/print/rows.inc.php:307]

305: function print_graph_summary_row($graph_array, $state_marker = FALSE)
306: {
307: echo(generate_graph_summary_row($graph_array, $state_marker));
{{308: }}}