Conditional column with null value error

Hello - you have to either filter out the nulls first, or use try-otherwise to step over them.

Filter out the nulls first would be like this:

= Table.AddColumn(#"Colunas Removidas1", "Status",
each if [DTENTREGA] = null or [DTPREVENT] = null then null
else if [DTENTREGA] < [DTPREVENT] then "Early"
else if [DTENTREGA] > [DTPREVENT] then "Late"
else if [DTENTREGA] = [DTPREVENT] then "On Time"
else if [DTENTREGA] = null then "In Progress"
else "Dispatch")

Using try-otherwise would be like this, but it is riskier since there could be other errors that are overstepped. 

= Table.AddColumn(#"Colunas Removidas1", "Status",
each try 
if [DTENTREGA] < [DTPREVENT] then "Early"
else if [DTENTREGA] > [DTPREVENT] then "Late"
else if [DTENTREGA] = [DTPREVENT] then "On Time"
else if [DTENTREGA] = null then "In Progress"
else "Dispatch" otherwise null)