title: cv2.error: OpenCV(4.5.2) .error: (-215:Assertion failed) !_src.empty() in function 'cv::cvtColor'
body: <pre class="lang-py prettyprint-override"><code>import cv2 #for image processing
  import easygui #to open the filebox
  import numpy as np #to store image
  import imageio #to read image stored at particular path
  
  import sys
  import matplotlib.pyplot as plt
  import os
  import tkinter as tk
  from tkinter import filedialog
  from tkinter import *
  from PIL import ImageTk, Image
  
  
  
  top=tk.Tk()
  top.geometry('400x400')
  top.title('Cartoonify Your Image !')
  top.configure(background='white')
  label=Label(top,background='#CDCDCD', font=('calibri',20,'bold'))
  
  def upload():
      ImagePath=easygui.fileopenbox()
      cartoonify(ImagePath)
  
  
  def cartoonify(ImagePath):
      
      # read the image
      originalmage = cv2.imread(ImagePath)
      
      originalmage = cv2.cvtColor(originalmage, cv2.COLOR_BGR2RGB)
      #print(image)  # image is stored in form of numbers
  </code></pre>
  <pre><code>cv2.error: OpenCV(4.5.2) C:\Users\runneradmin\AppData\Local\Temp\pip-req-build-vi271kac\opencv\modules\imgproc\src\color.cpp:182: error: (-215:Assertion failed) !_src.empty() in function 'cv::cvtColor'
  </code></pre>