patch 9.0.1333: when redo'ing twice <ScriptCmd> may not get the script ID

Problem:    When redo'ing twice <ScriptCmd> may not get the script ID.
Solution:   When "last_used_map" map is not set use "last_used_sid".
            (closes #11930)
diff --git a/src/getchar.c b/src/getchar.c
index 2f0079d..6645be8 100644
--- a/src/getchar.c
+++ b/src/getchar.c
@@ -3974,23 +3974,30 @@
 
 #if defined(FEAT_EVAL) || defined(PROTO)
 /*
- * If there was a mapping put info about it in the redo buffer, so that "."
- * will use the same script context.  We only need the SID.
+ * If there was a mapping we get its SID.  Otherwise, use "last_used_sid", it
+ * is set when redo'ing.
+ * Put this SID in the redo buffer, so that "." will use the same script
+ * context.
  */
     void
 may_add_last_used_map_to_redobuff(void)
 {
-    char_u buf[3 + 20];
+    char_u  buf[3 + 20];
+    int	    sid = -1;
 
-    if (last_used_map == NULL || last_used_map->m_script_ctx.sc_sid < 0)
+    if (last_used_map != NULL)
+	sid = last_used_map->m_script_ctx.sc_sid;
+    if (sid < 0)
+	sid = last_used_sid;
+
+    if (sid < 0)
 	return;
 
     // <K_SID>{nr};
     buf[0] = K_SPECIAL;
     buf[1] = KS_EXTRA;
     buf[2] = KE_SID;
-    vim_snprintf((char *)buf + 3, 20, "%d;",
-					   last_used_map->m_script_ctx.sc_sid);
+    vim_snprintf((char *)buf + 3, 20, "%d;", sid);
     add_buff(&redobuff, buf, -1L);
 }
 #endif
diff --git a/src/version.c b/src/version.c
index 0095489..b7fd23f 100644
--- a/src/version.c
+++ b/src/version.c
@@ -696,6 +696,8 @@
 static int included_patches[] =
 {   /* Add new patch number below this line */
 /**/
+    1333,
+/**/
     1332,
 /**/
     1331,