patch 8.2.4321: Vim9: crash when using a funcref to a closure

Problem:    Vim9: crash when using a funcref to a closure.
Solution:   Copy pt_outer to the new partial. (closes #9714)
diff --git a/src/evalfunc.c b/src/evalfunc.c
index 3cc95c9..eb12e75 100644
--- a/src/evalfunc.c
+++ b/src/evalfunc.c
@@ -4454,6 +4454,9 @@
 		    pt->pt_name = name;
 		    func_ref(name);
 		}
+
+		if (arg_pt != NULL)
+		    pt->pt_outer = arg_pt->pt_outer;
 	    }
 	    rettv->v_type = VAR_PARTIAL;
 	    rettv->vval.v_partial = pt;