Error when attempting to add a .tar file

Despite Settings=>Security=>Allowed File Settings:
aac,aif,aiff,asf,asx,avi,bmp,c,cc,class,css,divx,doc,docx,exe,gif,gz,gzip,h,ico,j2k,jp2,jpe,jpeg,jpg,m4a,mdb,mid,midi,mov,mp2,mp3,mp4,mpa,mpe,mpeg,mpg,mpp,odb,odc,odf,odg,odp,ods,odt,ogg, pdf,png,pot,pps,ppt,pptx,qt,ra,ram,rtf,rtx,swf,tar,tif,tiff,txt, wav,wax,wma,wmv,wmx,wri,xla,xls,xlsx,xlt,xlw,zip

I get this error when attempting to upload a tar:
[Tue Mar 15 09:56:25 2016] [error] [client] PHP Notice: Undefined index: tags in /var/www/html/legacy/application/libraries/Omeka/Controller/Pdmin/items/edit/13935

That notice isn't actually an error. Do you get any other messages?

no, however it appears in my httpd error log everytime I attempt with that particular item.

So there's no message from Omeka directly. What does happen when you try to add it? A normal failure (including a "this is a disallowed file type" error) would print a message at you immediately on the page. What page do you end up at?

Is the tar file quite large? If a file is so large that it's over the post_max_size PHP will basically throw out the whole request and leave you on the page you came from. That sounds like what might be happening here.

no, it is 2 MB and i have my server set to 24MB.