another small lineedit fix

Signed-off-by: Denys Vlasenko <vda.linux@googlemail.com>
diff --git a/libbb/lineedit.c b/libbb/lineedit.c
index a3d9395..9a773b4 100644
--- a/libbb/lineedit.c
+++ b/libbb/lineedit.c
@@ -429,7 +429,9 @@
 #endif
 
 	memmove(command_ps + j, command_ps + j + 1,
-			(command_len - j + 1) * sizeof(command_ps[0]));
+			/* (command_len + 1 [because of NUL]) - (j + 1)
+			 * simplified into (command_len - j) */
+			(command_len - j) * sizeof(command_ps[0]));
 	command_len--;
 	input_end();                    /* rewrite new line */
 	cmdedit_set_out_char(' ');      /* erase char */