Allow serving of 0-byte, real files

Essential for many HTTP challenges for domain verification, SSL cert issuance, etc.

public/.htaccess

@@ -1,7 +1,7 @@
 RewriteEngine On
 # The following rule tells Apache that if the requested filename
 # exists, simply serve it.
-RewriteCond %{REQUEST_FILENAME} -s [OR]
+RewriteCond %{REQUEST_FILENAME} -f [OR]
 RewriteCond %{REQUEST_FILENAME} -l [OR]
 RewriteCond %{REQUEST_FILENAME} -d
 RewriteRule ^.*$ - [NC,L]