patch 8.2.1862: vim9: memory leak when compiling lambda fails

Problem:    vim9: memory leak when compiling lambda fails.
Solution:   Call clear_evalarg().
diff --git a/src/vim9compile.c b/src/vim9compile.c
index edfa325..55368d1 100644
--- a/src/vim9compile.c
+++ b/src/vim9compile.c
@@ -2692,7 +2692,10 @@
 
     // Get the funcref in "rettv".
     if (get_lambda_tv(arg, &rettv, &evalarg) != OK)
+    {
+	clear_evalarg(&evalarg, NULL);
 	return FAIL;
+    }
 
     ufunc = rettv.vval.v_partial->pt_func;
     ++ufunc->uf_refcount;