Confusing Inspection Warning

I drafted this message when trying to understand why a warning is being thrown by a PyCharm inspection. I have the following simplified code:

array = [[1,2,3],[4,5,6],[7,8,9]]
print(array[1][1])
array[1][1] = 'data'
print(array[1][1])

It works as expected when I run it.  However, the inspection scanner complains about the second index...

Screen shot:

I assumed there was a problem with the type of the index.  It took me some time to realize that it was concerned about the change in data type. 

In the case I'm working with the code is changing None to a float.  Is there a preferred way to handle this?