Merge branch 'fix-srcname-cache-crash' into 'master'

update: don't crash if src tarball is not present

See merge request fdroid/fdroidserver!1691

fdroidserver/update.py

@@ -374,7 +374,8 @@ def get_cache():
             f = f'archive/{v["srcname"]}'
             if not os.path.exists(f):
                 f = f'repo/{v["srcname"]}'
-            v['srcnameSha256'] = common.sha256sum(f)
+            if os.path.exists(f):
+                v['srcnameSha256'] = common.sha256sum(f)
 
     return apkcache