W3m: out-of-bounds write in function checktype() in etc.c (incomplete fix for cve-2022-38223)

An out-of-bounds write issue has been discovered in the backspace handling of the checkType() function in etc.c within the W3M application. This vulnerability is triggered by supplying a specially crafted HTML file to the w3m binary. Exploitation of this flaw could lead to application crashes, resulting in a denial of service condition.