files: remove a superfluous condition, and do not ignore a "No"

Having just opened a fresh buffer, 'openfile->next' will never be NULL,
because the list is circular.

Second, when compiled with --disable-nultibuffer, and deciding not to
override an existing lock, the 'return FALSE' should *not* be skipped,
because otherwise the named file will be opened after all.

This fixes an unreported bug.

src/files.c

@@ -456,15 +456,14 @@ bool open_buffer(const char *filename, bool undoable)
 	if (has_valid_path(realname)) {
 #ifndef NANO_TINY
 	    if (ISSET(LOCKING) && filename[0] != '\0') {
+		/* When not overriding an existing lock, discard the buffer. */
 		if (do_lockfile(realname) < 0) {
 #ifndef DISABLE_MULTIBUFFER
-		    if (openfile->next) {
 		    close_buffer();
+#endif
 		    free(realname);
 		    return FALSE;
 		}
-#endif
-		}
 	    }
 #endif /* !NANO_TINY */
 	}