fix: VE.Direct MPPT data not always updated in websocket

set the "last published" timestampt after handling *all* MPPTs.

src/WebApi_ws_vedirect_live.cpp

@@ -138,9 +138,10 @@ void WebApiWsVedirectLiveClass::generateJsonResponse(JsonVariant& root, bool ful
         const JsonObject &nested = array.createNestedObject(serial);
         nested["data_age_ms"] = VictronMppt.getDataAgeMillis(idx);
         populateJson(nested, spMpptData);
-        _lastPublish = millis();
     }
 
+    _lastPublish = millis();
+
     // power limiter state
     root["dpl"]["PLSTATE"] = -1;
     if (Configuration.get().PowerLimiter.Enabled)