patch 9.0.2173: Vim9: crash when compiling for statement and non-existing type

Problem:  Vim9: Vim crashes when compiling a for statement with a
          non-existing type
Solution: Error out when  lhs_type is not null

closes: #13703

Signed-off-by: Yegappan Lakshmanan <yegappan@yahoo.com>
Signed-off-by: Christian Brabandt <cb@256bit.org>
diff --git a/src/vim9cmds.c b/src/vim9cmds.c
index 07e6501..a276d53 100644
--- a/src/vim9cmds.c
+++ b/src/vim9cmds.c
@@ -1088,6 +1088,8 @@
 		}
 		p = skipwhite(p + 1);
 		lhs_type = parse_type(&p, cctx->ctx_type_list, TRUE);
+		if (lhs_type == NULL)
+		    goto failed;
 	    }
 
 	    if (get_var_dest(name, &dest, CMD_for, &opt_flags,