adjust scrolling of `/nbextensions` config page so that it only occurs if the top of the extension settings panel isn't visible
adjust scrolling of `/nbextensions` config page so that it only occurs if the top of the extension settings panel isn't visible

original-commit-id: f28b8e2b1243d419d99b69e42a7c8fd6c752780e
original-commit-url: https://github.com/ipython-contrib/IPython-notebook-extensions/commit/f28b8e2b1243d419d99b69e42a7c8fd6c752780e

jcb91/jupyter_nbextensions_configurator,jcb91/jupyter_nbextensions_configurator,jcb91/jupyter_nbextensions_configurator,jcb91/jupyter_nbextensions_configurator