make deriver optional cause it won't be there if path is a derivation

src/path_info.rs

@@ -14,7 +14,7 @@ use url::Url;
 #[derive(Debug, Clone, Serialize, Deserialize)]
 #[serde(rename_all = "camelCase")]
 pub struct PathInfo {
-    pub deriver: StorePath<String>,
+    pub deriver: Option<StorePath<String>>,
     pub path: StorePath<String>,
     signatures: Vec<String>,
     pub references: Vec<StorePath<String>>,

src/uploader.rs

@@ -159,7 +159,7 @@ impl<'a> Uploader<'a> {
             signatures: Vec::new(),
             ca: None,
             system: None,
-            deriver: Some(self.path.deriver.as_ref()),
+            deriver: self.path.deriver.as_ref().map(|x| x.as_ref()),
             compression: Some("zstd"),
             file_hash: None,
             file_size: None,