patch 8.2.3444: concealed text not revealed when leaving insert mode

Problem:    concealed text not revealed when leaving insert mode. (Michael
            Soyka)
Solution:   Check if concealing changed when leaving insert mode.
            (closes #8880)
diff --git a/src/edit.c b/src/edit.c
index e1e796f..070d84c 100644
--- a/src/edit.c
+++ b/src/edit.c
@@ -3582,6 +3582,11 @@
 {
     int		temp;
     static int	disabled_redraw = FALSE;
+#ifdef FEAT_CONCEAL
+    // Remember if the cursor line was concealed before changing State.
+    int		cursor_line_was_concealed = curwin->w_p_cole > 0
+						&& conceal_cursor_line(curwin);
+#endif
 
 #ifdef FEAT_SPELL
     check_spell_redraw();
@@ -3701,6 +3706,11 @@
 	// Re-enable modifyOtherKeys.
 	out_str(T_CTI);
     }
+#ifdef FEAT_CONCEAL
+    // Check if the cursor line needs redrawing after changing State.  If
+    // 'concealcursor' is "i" it needs to be redrawn without concealing.
+    conceal_check_cursor_line(cursor_line_was_concealed);
+#endif
 
     // When recording or for CTRL-O, need to display the new mode.
     // Otherwise remove the mode message.