indenting: don't exclude last line of region when region is empty

This fixes https://savannah.gnu.org/bugs/?52717.

src/utils.c

@@ -540,7 +540,7 @@ void get_region(const filestruct **top, const filestruct **bot)
 
     mark_order(top, &top_x, bot, &bot_x, NULL);
 
-    if (bot_x == 0)
+    if (bot_x == 0 && *bot != *top)
 	*bot = (*bot)->prev;
 }