[syslinux] Missing Error Condition Check in core/fs/fs.c

[Shao Miller]

In 'core/fs/fs.c', 'fs.root' is set, but the 'iget_root' function 
pointer call might return a null pointer and we don't check for it.  A 
symptom was that QEmu crashed as EIP landed outside of memory.  - Shao


     /* start out in the root directory */
     if (fs.fs_ops->iget_root) {
         fs.root = fs.fs_ops->iget_root(&fs);
         /* Maybe we should check 'fs.root' here */
         fs.cwd = get_inode(fs.root);
     }