Remove unnecessary check if tok == NULL

This also corrects a formatting error (no space between the rparen of
the if and the lbrace of the code block).

src/vm_debug.c

@@ -75,10 +75,6 @@ vm_debug_next_arg(char **str)
     char *tok;
 
     while ((tok = strsep(str, " "))) {
-        if (tok == NULL) {
-            return NULL;
-        }
-
         if (*tok == '\0') {
             continue;
         }