PVS Studio reports: /usr/src/sys/geom/label/g_label_msdosfs.c:207:1: warning: V547 Expression 'sector0 != NULL' is always true.
Indeed, sector0 is being checked for NULL (with early return if it is) on line 75 in this function. However, the proposed patch also removes the check of sector because g_free() calls kernel free() which is documented to do nothing if the argument is NULL.