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.
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 when Openfire service is started.

2016.01.12 14:01:33 org.jivesoftware.openfire.container.PluginManager - Error loading plugin: C:\Openfire\plugins\loadstats
java.lang.NullPointerException
at org.apache.mina.management.MINAStatCollector.start(MINAStatCollector.java:129)
at org.jivesoftware.openfire.plugin.StatCollector.start(StatCollector.java:152)
at org.jivesoftware.openfire.plugin.StatisticPlugin.initializePlugin(StatisticPlug in.java:42)
at org.jivesoftware.openfire.container.PluginManager.loadPlugin(PluginManager.java :447)
at org.jivesoftware.openfire.container.PluginManager.access$300(PluginManager.java :68)
at org.jivesoftware.openfire.container.PluginManager$PluginMonitor.run(PluginManag er.java:1037)
at java.util.concurrent.Executors$RunnableAdapter.call(Unknown Source)
at java.util.concurrent.FutureTask.runAndReset(Unknown Source)
at java.util.concurrent.ScheduledThreadPoolExecutor$ScheduledFutureTask.access$301 (Unknown Source)
at java.util.concurrent.ScheduledThreadPoolExecutor$ScheduledFutureTask.run(Unknow n Source)
at java.util.concurrent.ThreadPoolExecutor.runWorker(Unknown Source)
at java.util.concurrent.ThreadPoolExecutor$Worker.run(Unknown Source)
at java.lang.Thread.run(Unknown Source)

thanks.