fix: discard polygons with length of 4 or less (#2100)

* discard polygons with length of 4 or less

* updated minimum length of polygons

* added line in CHANGELOG

Co-authored-by: Nikita Manovich <nikita.manovich@intel.com>

CHANGELOG.md

@@ -21,7 +21,7 @@ and this project adheres to [Semantic Versioning](https://semver.org/spec/v2.0.0
 -
 
 ### Fixed
--
+- Fixed multiple errors which arises when polygon is of length 5 or less (<https://github.com/opencv/cvat/pull/2100>)
 
 ### Security
 -
@@ -48,7 +48,6 @@ and this project adheres to [Semantic Versioning](https://semver.org/spec/v2.0.0
 - Fixed error with creating task with labels with the same name (<https://github.com/opencv/cvat/pull/2031>)
 - Django RQ dashboard view (<https://github.com/opencv/cvat/pull/2069>)
 - Object's details menu settings (<https://github.com/opencv/cvat/pull/2084>)
--
 
 ## [1.1.0-beta] - 2020-08-03
 ### Added

serverless/tensorflow/matterport/mask_rcnn/nuclio/model_loader.py

@@ -63,7 +63,7 @@ class ModelLoader:
                 contour = np.flip(contour, axis=1)
                 # Approximate the contour and reduce the number of points
                 contour = approximate_polygon(contour, tolerance=2.5)
-                if len(contour) < 3:
+                if len(contour) < 6:
                     continue
                 label = self.labels[class_id]