Power Query M language

Hi,

In my Power Query I am trying to combine two Columns into a new Custom column, which replaces only 'Null' values in 'Column 1' with values in 'Column 2'.

E.g
Title Column 1 Column 2 Custom Column
Amazon PS4 PS4 Games PS4
SGM Null PS4 Games PS4 Games


How do I achieve this desired result using the Power Query 'M' Language?

I am referencing this query in another query, which is why I cannot do this as a 'Calculated Column' in the Data Tab.

Thanks in advance,
Akash