Ignore them?

For me there is no way of knowing what they mean.
I got 4 notices that come back time and time again.
It has to do with the default_theme en the resource_db.php.

Does anybody have a clue?
These are the notices (looked at the resource_db.php but what should I change?

Notice [PHP]: Undefined index: default_theme in file class/smarty/plugins/resource.db.php line 17
Notice [PHP]: Undefined index: default_theme in file class/smarty/plugins/resource.db.php line 20
Notice [PHP]: Undefined index: default_theme in file class/smarty/plugins/resource.db.php line 71
Notice [PHP]: Undefined index: default_theme in file class/smarty/plugins/resource.db.php line 74
Notice [PHP]: Undefined variable: file_path in file class/smarty/plugins/resource.db.php line 96

some others are:
Notice [PHP]: Undefined offset: 3 in file modules/xoopsgallery/blocks/xoopsgallery_blocks.php line 52
Notice [PHP]: Undefined index: xoops_lblocks in file class/smarty/Smarty.class.php line 626

Thanks for your time and expertise.

erik