Correctly reset 'hide_children_in_tree'

Correctly reset the 'hide_children_in_tree' property to 0 when changing Resource Type coming from an empty Grid Container: {"gridclasskey":[]} (take note of the square brackets) or a Grid Container with some configs:  {"gridclasskey":{ /* grid configs here */ }} (we have curly brackets)
Merge pull request #60 from smanu85/patch-1

Correctly reset 'hide_children_in_tree'