quick fix for case when ssl_session_cache defined,
but ssl is not enabled in any server

src/core/ngx_cycle.c

diff --git a/src/core/ngx_cycle.c b/src/core/ngx_cycle.c
index eac6a5c..89109b3 100644
--- a/src/core/ngx_cycle.c
+++ b/src/core/ngx_cycle.c
@@ -373,6 +373,11 @@
             goto failed;
         }
 
+        if (shm_zone[i].init == NULL) {
+            /* unused shared zone */
+            continue;
+        }
+
         shm_zone[i].shm.log = cycle->log;
 
         opart = &old_cycle->shared_memory.part;