pound: zrealloc left half of split line when newline is inserted, too.

apps/pound.c

@@ -150,7 +150,8 @@ void editorInsertNewline(void) {
         if (!editorInsertRow(E.cy + 1, &row->chars[E.cx], row->size - E.cx))
             goto failed;
         row = &E.row[E.cy];   // reassign because zrealloc might have moved it
-        row->size = E.cx;   // xxx: zrealloc to free memory?
+        row->size = E.cx;
+        row->chars = zrealloc(row->chars, row->size + 1);
         row->chars[row->size] = '\0';
     }
     E.cy++;