[master] 108c65d37 Dont attempt to re-release the VCL

[Poul-Henning Kamp]

commit 108c65d37d1788b3e0f6ccc3e8837a7410ca39bb
Author: Poul-Henning Kamp <phk at FreeBSD.org>
Date:   Mon Apr 12 07:42:53 2021 +0000

    Dont attempt to re-release the VCL
    
    Fixes #3571

diff --git a/bin/varnishd/cache/cache_wrk.c b/bin/varnishd/cache/cache_wrk.c
index 090ada6c3..9b5d59c82 100644
--- a/bin/varnishd/cache/cache_wrk.c
+++ b/bin/varnishd/cache/cache_wrk.c
@@ -433,7 +433,7 @@ Pool_Work_Thread(struct pool *pp, struct worker *wrk)
 				else
 					tmo =  wrk->lastused+60.;
 				i = Lck_CondWait(&wrk->cond, &pp->mtx, tmo);
-				if (i == ETIMEDOUT)
+				if (i == ETIMEDOUT && wrk->vcl != NULL)
 					VCL_Rel(&wrk->vcl);
 				if (wrk->task->func != NULL) {
 					/* We have been handed a new task */