Wrong Tree count when removing interval corresponding to mid of interval tree

[AyushMittal1999]

Considering the following set of 10 intervals
var intervals = [[0, 1], [1, 2], [3, 4], [5, 6], [7, 8], [9, 10], [11, 12], [13, 14], [15, 16] ,[90, 100]];

When we try to remove interval [9, 10] which corresponds to root of interval tree (mid of root lies in this interval), the count of tree is updated to 8 instead of 9.

The wrong count occurs only when we have one interval belonging to root of the tree, and try to remove it.

[AyushMittal1999]

Have raised the fix for the issue, and request @mikolalysenko to please check the pull request