Added validity check for polygon similarity computation related to issue #2851 (#2852)

* Added validity check for polygon similarity computation

* Updated changelog

CHANGELOG.md

@@ -63,6 +63,7 @@ and this project adheres to [Semantic Versioning](https://semver.org/spec/v2.0.0
 - Fixed label editor name field validator (<https://github.com/openvinotoolkit/cvat/pull/2879>)
 - An error about track shapes outside of the task frames during export (<https://github.com/openvinotoolkit/cvat/pull/2890>)
 - Fixed project search field updating (<https://github.com/openvinotoolkit/cvat/pull/2901>)
+- Fixed export error when invalid polygons are present in overlapping frames (<https://github.com/openvinotoolkit/cvat/pull/2852>)
 
 ### Security
 

cvat/apps/dataset_manager/annotation.py

@@ -315,11 +315,14 @@ class ShapeManager(ObjectManager):
     @staticmethod
     def _calc_objects_similarity(obj0, obj1, start_frame, overlap):
         def _calc_polygons_similarity(p0, p1):
-            overlap_area = p0.intersection(p1).area
-            if p0.area == 0 or p1.area == 0: # a line with many points
-                return 0
+            if p0.is_valid and p1.is_valid: # check validity of polygons
+                overlap_area = p0.intersection(p1).area
+                if p0.area == 0 or p1.area == 0: # a line with many points
+                    return 0
+                else:
+                    return overlap_area / (p0.area + p1.area - overlap_area)
             else:
-                return overlap_area / (p0.area + p1.area - overlap_area)
+                return 0 # if there's invalid polygon, assume similarity is 0
 
         has_same_type  = obj0["type"] == obj1["type"]
         has_same_label = obj0.get("label_id") == obj1.get("label_id")