Root Cause Analysis: Looking at the given vulnerable code line and its context, the CWE-476 (NULL Pointer Dereference) vulnerability exists in the code because the `strlen` function is being called with the `display` pointer without first checking if it is NULL. If `display` is NULL, calling `strlen` with a NULL pointer will result in a NULL pointer dereference, causing a crash or undefined behavior.

To mitigate this vulnerability, the code should first check if `display` is not NULL before calling `strlen` on it.