jetbrains: make update script robust against if no channels exist

Co-authored-by: Weijia Wang <9713184+wegank@users.noreply.github.com>

pkgs/applications/editors/jetbrains/update_ides.py

@@ -31,6 +31,7 @@ def download_channels():
     return {
         channel["@name"]: channel
         for product in products
+        if "channel" in product
         for channel in one_or_more(product["channel"])
     }