vim-patch:8.2.3999: redundant check for NUL byte

Problem:    Redundant check for NUL byte.
Solution:   Remove the check for a NUL byte. (closes vim/vim#9471)
c024ed9233

src/nvim/ex_docmd.c

@@ -2897,7 +2897,7 @@ void f_fullcommand(typval_T *argvars, typval_T *rettv, FunPtr fptr)
     return;
   }
 
-  while (*name != NUL && *name == ':') {
+  while (*name == ':') {
     name++;
   }
   name = skip_range(name, NULL);