org.jivesoftware.util.Log - error drawing PDF footer

Dear Support,

it throws an error when viewing statistics reports.

2016.01.12 14:18:09 org.jivesoftware.util.Log - error drawing PDF footer: http://127.0.0.1:9090/plugins/monitoring/images/pdf_generatedbyof.gif is not a recognized imageformat.
2016.01.12 14:18:09 org.jivesoftware.util.Log - error drawing PDF footer: http://127.0.0.1:9090/plugins/monitoring/images/pdf_generatedbyof.gif is not a recognized imageformat.
2016.01.12 14:18:09 org.jivesoftware.util.Log - error drawing PDF footer: http://127.0.0.1:9090/plugins/monitoring/images/pdf_generatedbyof.gif is not a recognized imageformat.
2016.01.12 14:18:09 org.jivesoftware.util.Log - error drawing PDF footer: http://127.0.0.1:9090/plugins/monitoring/images/pdf_generatedbyof.gif is not a recognized imageformat.

somehow related to this error;

2016.01.12 14:01:33 org.jivesoftware.openfire.container.PluginManager - Error loading plugin: C:\Openfire\plugins\loadstats
java.lang.NullPointerException

Thanks.