Check more carefully for 'isFavorite' since it's not always there

Fixes #1058, see that issue for an example of a file where this would
throw an exception before.

src/icloudpd/xmp_sidecar.py

@@ -160,7 +160,7 @@ def build_metadata(asset_record: dict[str, Any]) -> XMPMetadata:
     ):
         rating = -1  # -1 means rejected: https://www.iptc.org/std/photometadata/specification/IPTC-PhotoMetadata#image-rating
     # only mark photo as favorite if not hidden or deleted
-    elif asset_record["fields"]["isFavorite"]["value"] == 1:
+    elif "isFavorite" in asset_record["fields"] and asset_record["fields"]["isFavorite"]["value"] == 1:
         rating = 5
 
     return XMPMetadata(

tests/test_xmp_sidecar.py

@@ -81,6 +81,11 @@ def test_build_metadata(self) -> None:
         metadata = build_metadata(assetRecordStub)
         assert metadata.Rating == 5
 
+        # Test favorites not present
+        del assetRecordStub["fields"]["isFavorite"]
+        metadata = build_metadata(assetRecordStub)
+        assert metadata.Rating is None
+
         # Test Deleted
         assetRecordStub["fields"]["isDeleted"]["value"] = 1
         metadata = build_metadata(assetRecordStub)