trying to reduce flickering

The NeoPixelBus RMT driver seems to get stalled when ESP.get.... functions are called (big kernel lock?). Also its glitching during flash file access.

This change tries to avoid some conflicts by first checking that the driver is not sending.

wled00/json.cpp

@@ -1032,6 +1032,14 @@ void serializeInfo(JsonObject root)
     if(ESP.getChipCores() > 1)    // WLEDMM
    	  root[F("resetReason1")] = (int)rtc_get_reset_reason(1);
   #endif
+
+  #if defined(ARDUINO_ARCH_ESP32)
+  unsigned long t_wait = millis();
+  while(strip.isUpdating() && (millis() - t_wait < 125)) delay(1); // WLEDMM try to catch a moment when strip is idle
+  while(strip.isUpdating() && (millis() - t_wait < 160)) yield();  //        try harder
+  //if (strip.isUpdating()) USER_PRINTLN("serializeInfo: strip still updating.");
+  #endif
+
   root[F("lwip")] = 0; //deprecated
   root[F("totalheap")] = ESP.getHeapSize(); //WLEDMM
   #else