Regex to handle empty views arguments is wrong

The regex in views.inc+33 appears to try to remove remaining %n arguments after all the substitutions are done. However, it has two problems.

First, I believe that \\/ should just be \/ as it's looking for a / and the single backslash is all that's needed to escape it. In the attached patch, I changed the substitutable character from slash to a comma, to fix the regex and make it easer to read.

Second, I think that you really want to find /%n and %n, so the / should be optional.