Merge pull request matplotlib#17025 from QuLogic/fix-nbagg-close

FIX: RecursionError when closing nbAgg figures.

Author: tacaswell

lib/matplotlib/_pylab_helpers.py

@@ -57,6 +57,8 @@ def destroy(cls, num):
             manager = num
             if cls.figs.get(manager.num) is manager:
                 cls.figs.pop(manager.num)
+            else:
+                return
         else:
             try:
                 manager = cls.figs.pop(num)