Fixes for probabilities

com.unity.perception/Editor/Randomization/VisualElements/Parameter/ParameterElement.cs

                     // First delete sets option to null, second delete removes option
                     var numOptions = optionsProperty.arraySize;
                     optionsProperty.DeleteArrayElementAtIndex(i);
+
+                    {
+                    }
+
+                    ResetProbabilities();
+
+            void ResetProbabilities()
+            {
+                var uniformProbability = probabilitiesProperty.arraySize > 0 ? 1f / probabilitiesProperty.arraySize : 0;
+                for (var i = 0; i < probabilitiesProperty.arraySize; i++)
+                {
+                    probabilitiesProperty.GetArrayElementAtIndex(i).floatValue = uniformProbability;
+                }
+            }
+
             listView.bindItem = BindItem;
 
             var addOptionButton = template.Q<Button>("add-option");
                         break;
                 }
 
+                ResetProbabilities();
+
                 m_SerializedProperty.serializedObject.ApplyModifiedProperties();
                 listView.itemsSource = categoricalParameter.probabilities;
                 listView.Refresh();
                         return;
                     var categories = LoadAssetsFromFolder(folderPath, categoricalParameter.sampleType);
 
-                    var probabilityIndex = probabilitiesProperty.arraySize;
-                    probabilitiesProperty.arraySize += categories.Count;
-
-                    var uniformProbability = 1f / categories.Count;
+                    probabilitiesProperty.arraySize += categories.Count;
+
-                        var probabilityProperty = probabilitiesProperty.GetArrayElementAtIndex(probabilityIndex + i);
-                        probabilityProperty.floatValue = uniformProbability;
+
+                    ResetProbabilities();
 
                     m_SerializedProperty.serializedObject.ApplyModifiedProperties();
                     listView.itemsSource = categoricalParameter.probabilities;