Ignore multipart/form-data parts without a Content-Disposition name

When parsing a multipart/form-data request with a MIME message which has
no "Content-Disposition" header (or a header without a name), then the
MIME-parser creates an empty part (no disposition, no disp_params - thus
no disp_params->name) and the post-request parser
Protocols.HTTP.Request->parse_post() converts the empty part into a query
variable with name 0 and an empty string as value: query = ([ 0: "" ]).
Trying to encode the resulting mapping to a query-string fails, because
Protocols.HTTP.http_encode_query(query) calls Protocols.HTTP->uri_encode()
on the key and the value and uri_encode() expects a non-zero string.

Example request without a Content-Disposition name:

  Content-Type: multipart/form-data; boundary=WxO

  --WxO

  --WxO--

lib/modules/Protocols.pmod/HTTP.pmod/Server.pmod/Request.pike

@@ -390,8 +390,8 @@ protected void parse_post()
     if(!messg->body_parts) return;
 
     foreach(messg->body_parts, object part) {
+      if(!part->disp_params->name) continue;
       if(part->disp_params->filename) {
-
 	if(variables[part->disp_params->name] && !arrayp(variables[part->disp_params->name]))
 	  variables[part->disp_params->name] = ({ variables[part->disp_params->name] });