title: geopandas overlay() function not working in QGIS
body: <p>I need to find the intersection of a GeoDataFrame with itself through geopandas in QGIS. The code works perfectly in the Anaconda environment but it fails in the QGIS python.</p>
  
  <p>Shapefile is available at below link:
  <a href="https://drive.google.com/file/d/1DQqg7Cf6AokyadkmOE8Y6k41tqDMXdmS/view?usp=drivesdk" rel="nofollow noreferrer">https://drive.google.com/file/d/1DQqg7Cf6AokyadkmOE8Y6k41tqDMXdmS/view?usp=drivesdk</a> </p>
  
  <p>Below is the code:</p>
  
  <pre><code>df1 = gpd.GeoDataFrame.from_file("C:\\QGIS_ShapeFile1\\qgis\\laneGroup.shp")
  intersection_gdf = overlay(df1, df1, how='intersection')
  </code></pre>
  
  <p>In QGIS, the following error occurs:</p>
  
  <pre><code>An error has occurred while executing Python code: 
  
  AttributeError: 'NoneType' object has no attribute 'intersection' 
  Traceback (most recent call last):
           File"C:/Users/sn43673/AppData/Roaming/QGIS/QGIS3\profiles\default/python/plugins\ad_qgis\shapefile_validator.py", line 318, in errorInShapeFile
      intersection_gdf = overlay(df1, df2, how='intersection')File "C:\PROGRA~1\QGIS3~1.6\apps\Python37\lib\site-packages\geopandas\tools\overlay.py", line 391, in overlay
    File "C:\PROGRA~1\QGIS3~1.6\apps\Python37\lib\site-packages\geopandas\tools\overlay.py", line 216, in _overlay_intersection
      for k in j:
    File "C:\PROGRA~1\QGIS3~1.6\apps\Python37\lib\site-packages\pandas\core\series.py", line 4042, in apply
      mapped = lib.map_infer(values, f, convert=convert_dtype)
    File "pandas\_libs\lib.pyx", line 2228, in pandas._libs.lib.map_infer
    File "C:\PROGRA~1\QGIS3~1.6\apps\Python37\lib\site-packages\geopandas\tools\overlay.py", line 216, in 
      for k in j:
  AttributeError: 'NoneType' object has no attribute 'intersection'
  </code></pre>