Error message: Whitespace is not allowed at this location

Question

Hi,
While hoovering over a function name in a C# code, I get the following tooltip message:

"XML comment contains invalid XML: Whitespace is not allowed at this location".

I can not find a way to locate that whitespace location, while running the function gives me 'object reference not set' exception message.

I am not sure if those are related to each other, but clearly I would like to fix the error.
Can anyone help?