fix sum_total_duration failing if duration_seconds is not an int (#598)

* fix sum_total_duration failing if duration_seconds is not an int

Signed-off-by: Adwait Thattey <coderdude1999@gmail.com>

* format

---------

Signed-off-by: Adwait Thattey <coderdude1999@gmail.com>
Co-authored-by: sigma67 <sigma67.github@gmail.com>

ytmusicapi/helpers.py

@@ -71,4 +71,11 @@ def to_int(string):
 def sum_total_duration(item):
     if "tracks" not in item:
         return 0
-    return sum([track["duration_seconds"] if "duration_seconds" in track else 0 for track in item["tracks"]])
+    return sum(
+        [
+            track["duration_seconds"]
+            if ("duration_seconds" in track and isinstance(track["duration_seconds"], int))
+            else 0
+            for track in item["tracks"]
+        ]
+    )