title: FSCalendar content getting squished when I switch scope to month
body: <p>My FSCalendar's content shrinks when I switch its scope from week to month if there is a view that's constrained to its bottom anchor.</p>
  
  <p><strong>Here is a quick gif to show what exactly is happening</strong></p>
  
  <p><img src="https://i.stack.imgur.com/8PtQv.gif" alt="GIF"></p>
  
  <p>I have tried everything at this point. Using <code>calendar.setScope()</code> instead of <code>calendar.scope =</code>, constraining <code>attachedToCalendarView.topAnchor</code> to <code>calendar.bottomAnchor</code> <code>calendar.contentView.bottomAnchor</code>, and <code>calendar.daysContainer.bottomAnchor</code>, even turning <code>attachedToCalendarView</code> 's constraints on and off depending on whether it's week scope or scope month. </p>
  
  <p>Not sure what else to try. Here is the code: </p>
  
  <pre><code>import UIKit
  import FSCalendar
  
  class TestController : UIViewController, FSCalendarDataSource, FSCalendarDelegate, FSCalendarDelegateAppearance {
  
  fileprivate weak var calendar: FSCalendar!
  
  override func viewDidLoad() {
      super.viewDidLoad()
      view.backgroundColor = .white
      setUp()
  }
  
  
  @objc func switchCalendarScope(){
      if self.calendar.scope == FSCalendarScope.month {
          self.calendar.scope = FSCalendarScope.week
  
      } else {
          self.calendar.scope = FSCalendarScope.month
      }
  
  }
  
  func setUp(){
  
      let calendar = FSCalendar()
      calendar.dataSource = self
      calendar.delegate = self
      self.calendar = calendar
  
      self.calendar.scope = .week
      self.calendar.locale = Locale(identifier: "en_EN")
      self.calendar.calendarHeaderView.calendar.locale =  Locale(identifier: "en_EN")
      self.calendar.adjustsBoundingRectWhenChangingMonths = true
  
      let testingView = UIView()
      testingView.backgroundColor = .red
  
      let attachedToCalendarView = UIView()
      attachedToCalendarView.backgroundColor = .blue
  
      view.addSubview(calendar)
      view.addSubview(testingView)
      view.addSubview(attachedToCalendarView)
  
      self.calendar.translatesAutoresizingMaskIntoConstraints = false
      self.calendar.centerXAnchor.constraint(equalTo: view.centerXAnchor).isActive = true
      self.calendar.topAnchor.constraint(equalTo: view.safeAreaLayoutGuide.topAnchor).isActive = true
      self.calendar.widthAnchor.constraint(equalToConstant: view.bounds.size.width).isActive = true
      self.calendar.heightAnchor.constraint(equalToConstant: 300).isActive = true
  
      testingView.translatesAutoresizingMaskIntoConstraints = false
      testingView.centerXAnchor.constraint(equalTo: view.centerXAnchor).isActive = true
      testingView.widthAnchor.constraint(equalToConstant: view.bounds.size.width).isActive = true
      testingView.heightAnchor.constraint(equalToConstant: 20).isActive = true
  
      attachedToCalendarView.translatesAutoresizingMaskIntoConstraints = false
      attachedToCalendarView.centerXAnchor.constraint(equalTo: view.centerXAnchor).isActive = true
      // Attaching this view's topAnchor to the calendar's bottom anchor
      attachedToCalendarView.topAnchor.constraint(equalTo: self.calendar.contentView.bottomAnchor).isActive = true
      attachedToCalendarView.widthAnchor.constraint(equalToConstant: view.bounds.size.width).isActive = true
      attachedToCalendarView.heightAnchor.constraint(equalToConstant: 20).isActive = true
  
  
      // Title and button to toggle the calendar scope
      self.navigationItem.title = "Test"
      self.navigationItem.rightBarButtonItem = UIBarButtonItem(title: "Toggle", style: .done, target: self, action: #selector(switchCalendarScope))
  }
  </code></pre>
  
  <p>}</p>