Blackpill using Arduino IDE

Good day all, I would like to ask, can analogRead be used in the Arduino IDE to read the reading from the MQ-2 gas sensor? When I unplug the sensor, the reading should be 0, but the LCD still shows a value. How can I fix it?

Here are my code,

#include <LiquidCrystal_I2C.h>

#define gasSensorPin PA0
#define buzzerPin PB2

LiquidCrystal_I2C lcd(0x27,16,2);
void setup() {
 // put your setup code here, to run once:
 lcd.init();
 lcd.backlight();

 Serial.begin(9600);
 pinMode(gasSensorPin,INPUT);
 pinMode(buzzerPin,OUTPUT);
}

void loop() {
 // put your main code here, to run repeatedly:
 int sensorValue = analogRead(gasSensorPin); // Read the analog value from the gas sensor
 
 // Display the readings on the LCD
 lcd.setCursor(0, 0);
 lcd.print("Gas Sensor:");
 lcd.print(sensorValue);


 if(sensorValue>15){
 digitalWrite(buzzerPin,HIGH);
 }
 else{
 digitalWrite(buzzerPin,LOW);
 }

 delay(1000);
}

thanks.