lineedit: histfile can get emptied when CONFIG_FEATURE_EDITING_SAVE_ON_EXIT=y

When CONFIG_FEATURE_EDITING_SAVE_ON_EXIT is set to y, the histfile
will get cleared if the total amount of history lines is less than MAX_HISTORY.
Only if the histfile is not empty _and_ the amount of lines currently
in memory are equal to or greater than MAX_HISTORY, history saving will
work as expected with this feature enabled.

Output from defconfig + CONFIG_FEATURE_EDITING_SAVE_ON_EXIT=y:
$ echo "foo" > ~/.ash_history
$ ./busybox ash
~/busybox/a $ echo "bar" > /dev/null
~/busybox/a $ exit
$ cat ~/.ash_history
$

Output with the patch applied and same config as above:
$ echo "foo" > ~/.ash_history
$ ./busybox ash
~/busybox/b $ echo "bar" > /dev/null
~/busybox/b $ exit
$ cat ~/.ash_history
foo
echo "bar" > /dev/null
exit
$

Signed-off-by: Dennis Groenen <tj.groenen at gmail.com>
Signed-off-by: Denys Vlasenko <vda.linux@googlemail.com>
diff --git a/libbb/lineedit.c b/libbb/lineedit.c
index db84167..b89748a 100644
--- a/libbb/lineedit.c
+++ b/libbb/lineedit.c
@@ -1352,8 +1352,7 @@
 		/* fill temp_h[], retaining only last MAX_HISTORY lines */
 		memset(temp_h, 0, sizeof(temp_h));
 		idx = 0;
-		if (!ENABLE_FEATURE_EDITING_SAVE_ON_EXIT)
-			st_parm->cnt_history_in_file = 0;
+		st_parm->cnt_history_in_file = 0;
 		while ((line = xmalloc_fgetline(fp)) != NULL) {
 			if (line[0] == '\0') {
 				free(line);
@@ -1361,8 +1360,7 @@
 			}
 			free(temp_h[idx]);
 			temp_h[idx] = line;
-			if (!ENABLE_FEATURE_EDITING_SAVE_ON_EXIT)
-				st_parm->cnt_history_in_file++;
+			st_parm->cnt_history_in_file++;
 			idx++;
 			if (idx == st_parm->max_history)
 				idx = 0;