message: fix panic if crate failed to build
  closes
  gives a 404 if you try to view the source
diff: @@ -104,7 +104,7 @@ impl FileList {
  return None;
  }
  - let files: Json = rows.get(0).get(5);
  + let files: Json = rows.get(0).get_opt(5).unwrap().ok()?;
  let mut file_list: Vec<File> = Vec::new();
  @@ -181,6 +181,8 @@ impl FileList {
  pub fn source_browser_handler(req: &mut Request) -> IronResult<Response> {
  + use iron::status;
  + use super::error::Nope;
  let router = extension!(req, Router);
  let name = cexpect!(router.find("name"));
  let version = cexpect!(router.find("version"));
  @@ -246,6 +248,6 @@ pub fn source_browser_handler(req: &mut Request) -> IronResult<Response> {
  .set_bool("file_content_rust_source", is_rust_source)
  .to_resp("source")
  } else {
  - page.to_resp("source")
  + Err(IronError::new(Nope::CrateNotFound, status::NotFound))
  }
  }
  