chore: capture the error while create new healthchecker (#3213)

fix #3169

Author: dabue

apisix/balancer.lua

@@ -87,12 +87,17 @@ local function create_checker(upstream, healthcheck_parent)
     if healthcheck == nil then
         healthcheck = require("resty.healthcheck")
     end
-    local checker = healthcheck.new({
+    local checker, err = healthcheck.new({
         name = "upstream#" .. healthcheck_parent.key,
         shm_name = "upstream-healthcheck",
         checks = upstream.checks,
     })
 
+    if not checker then
+        core.log.error("fail to create healthcheck instance: ", err)
+        return
+    end
+
     local host = upstream.checks and upstream.checks.active and upstream.checks.active.host
     local port = upstream.checks and upstream.checks.active and upstream.checks.active.port
     for _, node in ipairs(upstream.nodes) do