title: Creating a centroid column from geometry shape field produces AttributeError: 'NoneType' object has no attribute 'centroid'
body: <p>I have imported a shape file of Australian local government areas (LGA's) into google Colab and successfully read into geopandas. The subsequent geodataframe </p>
  
  <pre><code>lga_df = gpd.read_file("LGA_2016_AUST.shp")
  </code></pre>
  
  <p>has a geometry field with a list of polygons. I am trying to find the centroid / lat &amp; long point  in order to use the LGA names as labels in the map I will create. </p>
  
  <p>The code I am using to create the centroid field is</p>
  
  <pre><code> lga_df["center"] = lga_df["geometry"].centroid
   lga_df_points = lga_df.copy()
   lga_df_points.set_geometry("center", inplace = True)
  </code></pre>
  
  <p>Logic is </p>
  
  <p>copy the original df_lga to a new df, and then set 
  the geometry column to the newly created center points column 
  because a GeoPandas df can only have one geometry column)</p>
  
  <p>However, I am getting the following message</p>
  
  <pre><code>AttributeError: 'NoneType' object has no attribute 'centroid'. 
  </code></pre>
  
  <p>I have also tried code using representative_point() but doesn;t work either</p>
  
  <p>I believe I have imported all the necessary dependencies - (see below)  </p>
  
  <pre><code>import geopandas as gpd
  from geopandas import GeoDataFrame
  import pandas as pd 
  import matplotlib.pyplot as plt
  %matplotlib inline
  from shapely.geometry import Point, LineString
  import adjustText as aT
  </code></pre>
  
  <p>I have tried for a few hours but still get same error. Can someone advise where I am going wrong</p>
  
  <hr>
  
  <p>Update - This Problem has been solved - geometry field had rows with No polygon co-ordinates. I have removed the rows without polygon coordinates. However, another error is thrown out. "Attribute error - Series does not have the attribute 'centroid'. 
  I am thinking for some reason python is not recognising my geometry field as a geometry field but text / string field. How do I convert a geometry field that is a string to a geometry field?    </p>