patch 8.2.0280: Vim9: throw in :def function not caught higher up

Problem:    Vim9: throw in :def function not caught higher up.
Solution:   Set "need_rethrow".
diff --git a/src/vim9execute.c b/src/vim9execute.c
index 4555748..4349489 100644
--- a/src/vim9execute.c
+++ b/src/vim9execute.c
@@ -482,6 +482,7 @@
 		    tv->v_type = VAR_NUMBER;
 		    tv->vval.v_number = 0;
 		    ++ectx.ec_stack.ga_len;
+		    need_rethrow = TRUE;
 		    goto done;
 		}