file: moodle \ lib \ upgradelib.php
function: function upgrade_plugin_mnet_functions ($ component)
line: list ($ type, $ plugin) = explode ('_', $ component);

If a plugin or block, etc. have a two-membered name eg "block_my_courses"
the variable $plugin substituted is set to 'my' and should be 'my_courses'

Should look like: list ($ type, $ plugin) = normalize_component ($ component);