You could leave it as it is and it shouldn't cause any problems. The indexignore statement prevents a directory listing if there isn't an index file in the directory. I think what is causing the problem is the last 5 lines, the 4 rewritecond and the rewriterule.

You can test it by putting a pound sign on the beginning of each of those lines:

#RewriteCond ....
#RewriteCond ....
#RewriteCond ....
#RewriteCond ....
#RewriteRule ...

and saving it. Then you can rename the .htaccess file back to .htaccess and see if it work. The pound sign indicates a comment and will ignore what is after on the rest of the line. This is convenient so you can make comments in a file to explain what something does for quick reference.