How to handle Firefox print dialog box in Selenium

I have the following code:

from selenium.webdriver import Firefox
from selenium.webdriver.common.keys import Keys
url = 'https://finance.yahoo.com/'
driver_path = 'geckodriver.exe'

browser = Firefox(executable_path = driver_path)
browser.get(url)
profile.set_preference("browser.helperApps.neverAsk.saveToDisk", "application/pdf")
profile.set_preference("browser.helperApps.neverAsk.openFile", "application/pdf")
search_field_id = 'yfin-usr-qry'

element_search_field = browser.find_element_by_id(search_field_id)
element_search_field.clear()
element_search_field.send_keys('TSLA')
element_search_field.send_keys(Keys.ENTER)
from selenium.webdriver import ActionChains
action_chains = ActionChains(browser)
action_chains.key_down(Keys.CONTROL).send_keys('V').key_up(Keys.CONTROL).perform()
xpath_string = '/html/body/div[1]/div/div/div[1]/div/div[2]/div/div/div[6]/div/div/section/div/ul/li[2]/a/span'
element = browser.find_element_by_xpath(xpath_string)
action_chains.move_to_element(element).click().perform()
browser.execute_script('window.print();')

A print dialog box pops up for Firefox. I was wondering how can i accept it. Is there a way to bypass this dialog box and directly print since this is not a system dialog box but Firefox's.

Edit: My full updated code as per input from @Prophet

from selenium.webdriver import Firefox
from selenium.webdriver.common.keys import Keys
from selenium.webdriver import ActionChains
from selenium.webdriver.support.ui import Select
from selenium.webdriver.firefox.options import Options
from selenium.webdriver.firefox.firefox_profile import FirefoxProfile
import time
from fake_useragent import UserAgent
from selenium import webdriver
from selenium.webdriver import DesiredCapabilities
from selenium.common.exceptions import NoSuchElementException
from selenium.webdriver.common.keys import Keys
ua = UserAgent()
userAgent = ua.random

url = 'https://finance.yahoo.com/'
driver_path = 'geckodriver.exe'

profile = FirefoxProfile('C:\\Users\\\\AppData\\Roaming\\Mozilla\\Firefox\\Profiles\\tp3cz5dm.default-release')
profile.set_preference("general.useragent.override", userAgent)

browser = Firefox(executable_path = driver_path)
browser.get(url)
profile.set_preference("browser.helperApps.neverAsk.saveToDisk", "application/pdf")
profile.set_preference("browser.helperApps.neverAsk.openFile", "application/pdf")
search_field_id = 'yfin-usr-qry'

element_search_field = browser.find_element_by_id(search_field_id)
element_search_field.clear()
element_search_field.send_keys('TSLA')
element_search_field.send_keys(Keys.ENTER)
from selenium.webdriver import ActionChains
action_chains = ActionChains(browser)
action_chains.key_down(Keys.CONTROL).send_keys('V').key_up(Keys.CONTROL).perform()
# xpath_string = '/html/body/div[1]/div/div/div[1]/div/div[2]/div/div/div[6]/div/div/section/div/ul/li[2]/a/span'
# element = browser.find_element_by_xpath(xpath_string)
# action_chains.move_to_element(element).click().perform()
browser.execute_script('window.print();')

browser.switch_to.window(browser.window_handles[-1])
time.sleep(0.5)
actionButton = browser.execute_script(
"return document.querySelector('print-preview-app').shadowRoot.querySelector('#sidebar').shadowRoot.querySelector('print-preview-button-strip').shadowRoot.querySelector('.action-button')")
cancelButton.click()
# switch back to main window
browser.switch_to.window(driver.window_handles[0])

When i run this i am getting error:

JavascriptException: TypeError: document.querySelector(...) is null

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