patch 8.2.1070: Vim9: leaking memory when lacking white space in dict

Problem:    Vim9: leaking memory when lacking white space in dict.
Solution:   Clear the typval.
diff --git a/src/dict.c b/src/dict.c
index 748a991..be3282d 100644
--- a/src/dict.c
+++ b/src/dict.c
@@ -862,6 +862,7 @@
 	if (vim9script && (*arg)[1] != NUL && !VIM_ISWHITE((*arg)[1]))
 	{
 	    semsg(_(e_white_after), ":");
+	    clear_tv(&tvkey);
 	    goto failret;
 	}