BUG/MAJOR: lua segmentation fault when the request is like 'GET ?arg=val HTTP/1.1'

BUG/MAJOR: lua segmentation fault when the request is like 'GET ?arg=val HTTP/1.1'

Error in the HTTP parser. The function http_get_path() can
return NULL and this case is not catched in the code. So, we
try to dereference NULL pointer, and a segfault occurs.

These two lines are useful to prevent the bug.

   acl prevent_bug path_beg /
	http-request deny if !prevent_bug

This bug fix should be backported in 1.6 and 1.7