fix for exception on unhandled heic box hdlr (#228)

Author: ianare

exifread/core/heic.py

@@ -328,10 +328,13 @@ def _parse_iref(self, box: Box) -> None:
 
     def find_exif(self) -> Tuple[int, bytes]:
         ftyp = self.expect_parse("ftyp")
-        assert ftyp.major_brand == b"heic"
-        assert ftyp.minor_version == 0
+        if ftyp.major_brand != b"heic" or ftyp.minor_version != 0:
+            return 0, b""
+
         meta = self.expect_parse("meta")
-        assert meta.subs["iinf"].exif_infe is not None
+        if meta.subs["iinf"].exif_infe is None:
+            return 0, b""
+
         item_id = meta.subs["iinf"].exif_infe.item_id
         extents = meta.subs["iloc"].locs[item_id]
         logger.debug("HEIC: found Exif location.")

tests/resources/dump

@@ -1,3 +1,6 @@
+Opening: tests/resources/heic/heic_hdlr_box.jpg
+No EXIF information found
+
 Opening: tests/resources/heic/mobile/HMD_Nokia_8.3_5G.heif
 EXIF ExposureProgram (Short): Unidentified
 EXIF ExposureTime (Ratio): 1/5000