setValue hangs (freeze) if device with address is not connected about mcp4725 HOT 13 CLOSED

#include <Wire.h>
#include <ESP8266WiFi.h>
#include <PubSubClient.h>
#include "PCF8591.h"
#include "MCP4725.h"
#define OUTPUTS_N 2
#define INPUTS_N 1

const char* ssid = "--------------";
const char* password = "-----------";
const char* mqtt_server = "------------";

WiFiClient espClient;
PubSubClient client(espClient);
const char* lightsTopicName = "lights/hall/";
int lightTopicLenght = 12;
char msg[50];

// I/O units
struct InputUnit {
  int id;     // used for mqtt
  int multiplex;  // address of multiplexer
  int bus;        // bus 0-7
  int port;       // 0 - 4, typical 2
  PCF8591 driver;  
  int value;
};

struct OutputUnit {
  int id;     // used for mqtt
  int multiplex;  // address of multiplexer
  int bus;        // bus 0-7
  int type;       // 1 PCF8591, 2 MCP4725
  PCF8591 pcf;  
  MCP4725 mcp;
  int value;
  int target;
};


struct InputUnit hall_1_1 = {1, 0x70, 0,  2,  PCF8591(0x48),0};
struct InputUnit inputs[INPUTS_N] = {hall_1_1};

struct OutputUnit hall_3 = {1,0x70,0,1, PCF8591(0x48),(MCP4725)NULL ,0,255};
struct OutputUnit hall_2 = {2,0x70,1,2,(PCF8591)NULL,  MCP4725(0x61),0,255};

struct OutputUnit outputs[OUTPUTS_N] = {hall_2,hall_3};

void setup_wifi() {
  delay(10);
  Serial.println();
  Serial.print("Connecting to ");
  Serial.println(ssid);
  WiFi.begin(ssid, password);
  while (WiFi.status() != WL_CONNECTED) {
    delay(500);
    Serial.print(".");
  }

  randomSeed(micros());
  Serial.println("IP address: ");
  Serial.println(WiFi.localIP());
}

void callback(char* topic, byte* payload, unsigned int length) {
  Serial.print("Message arrived [");
  Serial.print(topic);
  Serial.print("] ");
  for (int i = 0; i < length; i++) {
    Serial.print((char)payload[i]);
  }
  Serial.println();
  int id = String(topic).substring(lightTopicLenght).toInt();
  Serial.print("Light  #");
  Serial.print(id);
  Serial.print(" target:");
   
  for(int i =0; i<OUTPUTS_N;i++){
    if(outputs[i].id == id){
       outputs[i].target=String((char*)payload).substring(0,length).toInt();
       Serial.println(outputs[i].target);
      break;
    }
  }
}

void reconnect() {
  // Loop until we're reconnected
  while (!client.connected()) {
    Serial.print("Attempting MQTT connection...");
    // Create a random client ID
    String clientId = "ESP8266Client-";
    clientId += String(random(0xffff), HEX);
    // Attempt to connect
    if (client.connect(clientId.c_str())) {
       for(int i=0;i<OUTPUTS_N;i++){
        client.subscribe((char*) String(String(lightsTopicName)+String(outputs[i].id)).c_str());
        Serial.print("Subscribe to: \t");
        Serial.println(outputs[i].id);
      }
    } else {
      Serial.print("failed, rc=");
      Serial.print(client.state());
      Serial.println(" try again in 5 seconds");
      // Wait 5 seconds before retrying
      delay(5000);
    }
  }
}

void busSelect(int addr,int i) {
  if (i > 7) return;
  Wire.beginTransmission(addr);
  Wire.write(1 << i);
  Wire.endTransmission();  
}

int step(int diff){
  if(diff == 0) return 0;
  if(diff  <0) return -1;
  if(diff  >0) return 1;
}

void setup() {
  Serial.begin(115200);
  setup_wifi();
  client.setServer(mqtt_server, 1883);
  client.setCallback(callback);
}

void loop() {
 if (!client.connected()) {
  reconnect();
  }
  client.loop();
  
  for(int i=0;i<INPUTS_N;i++){
      InputUnit input = inputs[i];
      busSelect(input.multiplex,input.bus);
      input.driver.begin();
      int val = input.driver.analogRead(2);
      snprintf (msg, 10, "pirs/%ld", input.id);
      if(inputs[i].value != val){
        inputs[i].value= val;
        client.publish((char*)  String("pirs/"+String(input.id)).c_str(), (char*) String(val).c_str());    
        Serial.print("Publish message: ");
        Serial.print(msg);
        Serial.print(":");
        Serial.println(inputs[i].value);
  }
  }

  for(int i=0;i<2;i++){
    OutputUnit output = outputs[i];
    busSelect(output.multiplex,output.bus);   
    int diff = step(output.target-output.value);
    outputs[i].value = outputs[i].value+diff ;
   
    if(diff != 0 ){
      
      switch(output.type){
        case 1:
          Serial.println("PCF");
          output.pcf.begin();
          output.pcf.analogWrite(output.value);
        break;
        case 2:
          Serial.println("MCP");
          output.mcp.begin();
          output.mcp.setValue(output.value*16-1);
        break;
      }
    }
  }
  delay(1);
}