eina_vpath: add null checking logic on vpath_resolve api

Summary:
there is a patch that add vpath_resolve() call before eina_file_open()
because `path` arg could be NULL, the patch kills some applications.
this patch add null checking logic on vpath_resolve api

Reviewers: bu5hm4n, cedric, Hermet

Reviewed By: Hermet

Subscribers: #reviewers, #committers

Tags: #efl

Differential Revision: https://phab.enlightenment.org/D9748

src/lib/eina/eina_vpath.c

@@ -327,6 +327,7 @@ EAPI char *
 eina_vpath_resolve(const char* path)
 {
    char buf[PATH_MAX];
+   EINA_SAFETY_ON_NULL_RETURN_VAL(path, NULL);
 
    if (_eina_vpath_resolve(path, buf, sizeof(buf)) > 0)
      return strdup(buf);