efl_ui_focus_manager: Add null check

Summary:
This commit add null check on _next and _request_subchild function.
The value 'node' is can be null.

Test Plan: N/A

Reviewers: bu5hm4n, YOhoho, Hermet

Reviewed By: Hermet

Subscribers: cedric, #reviewers, #committers

Tags: #efl

Differential Revision: https://phab.enlightenment.org/D7069

src/lib/elementary/efl_ui_focus_manager_calc.c

@@ -1111,6 +1111,7 @@ static Node*
 _next(Node *node)
 {
    Node *n;
+   if (!node) return NULL;
 
    //Case 1 we are having children
    //But only enter the children if it does NOT have a redirect manager
@@ -1295,6 +1296,7 @@ _request_subchild(Node *node)
 {
    //important! if there are no children _next would return the parent of node which will exceed the limit of children of node
    Node *target = NULL;
+   if (!node) return target;
 
    if (node->tree.children)
      {