problem with translation update procedure


I am using the Google+ plugin on my WP network in a french version.

I made my own translation (not taken from your translation repository because of particular needs) and now, with the today upgrade of the plugin, some strings are of course missing in my .po file.

I tried to make a new .pot file using the POEDIT PRO 'translate wordpress theme or plugin' feature, so that I could then after update my .po file with it but when I select the Google+ plugin source folder (google-analytics-async), I get an error on POEDIT:

no matches for "load_plugin_textdomains*(s*['"]([^'"]+)['"]s*, "
no load_plugin_textdomain call and lacking metadata

Could this problem be fixed, or is there an other safe way to update my .po file ?