Fix 500 when an event thumbnail file is empty (#24110)

* fix 500 when an event thumbnail file is empty

* fix test

frigate/api/media.py

@@ -1060,7 +1060,7 @@ async def event_thumbnail(
     except DoesNotExist:
         thumbnail_bytes = None
 
-    if thumbnail_bytes is None:
+    if not thumbnail_bytes:
         # see if the object is currently being tracked
         try:
             camera_states = request.app.detected_frames_processor.get_camera_states()
@@ -1076,7 +1076,7 @@ async def event_thumbnail(
                 status_code=404,
             )
 
-    if thumbnail_bytes is None:
+    if not thumbnail_bytes:
         return JSONResponse(
             content={"success": False, "message": "Event not found"},
             status_code=404,
@@ -1085,6 +1085,13 @@ async def event_thumbnail(
     img_as_np = np.frombuffer(thumbnail_bytes, dtype=np.uint8)
     img = cv2.imdecode(img_as_np, flags=1)
 
+    if img is None:
+        # thumbnail on disk is truncated or corrupt
+        return JSONResponse(
+            content={"success": False, "message": "Event not found"},
+            status_code=404,
+        )
+
     # android notifications prefer a 2:1 ratio
     if format == "android":
         img = cv2.copyMakeBorder(

frigate/test/test_file.py

@@ -70,3 +70,19 @@ class TestFileUtils(TestCase):
             assert rendered_image is not None
             assert rendered_image.shape[0] == 40
             assert rendered_image.max() > 0
+
+    def test_get_event_thumbnail_bytes_ignores_empty_file(self):
+        """Verify empty thumbnail files are treated as missing."""
+        event = SimpleNamespace(id="empty-thumb", camera="front_door", thumbnail=None)
+
+        with (
+            tempfile.TemporaryDirectory() as thumb_dir,
+            patch.object(file_util, "THUMB_DIR", thumb_dir),
+        ):
+            camera_dir = os.path.join(thumb_dir, event.camera)
+            os.makedirs(camera_dir)
+
+            with open(os.path.join(camera_dir, f"{event.id}.webp"), "wb"):
+                pass
+
+            assert file_util.get_event_thumbnail_bytes(event) is None

frigate/util/file.py

@@ -20,14 +20,15 @@ logger = logging.getLogger(__name__)
 
 
 def get_event_thumbnail_bytes(event: Event) -> bytes | None:
+    # callers treat empty bytes as a valid image, so normalize them to None
     if event.thumbnail:
-        return base64.b64decode(event.thumbnail)
+        return base64.b64decode(event.thumbnail) or None
     else:
         try:
             with open(
                 os.path.join(THUMB_DIR, event.camera, f"{event.id}.webp"), "rb"
             ) as f:
-                return f.read()
+                return f.read() or None
         except Exception:
             return None