If you have assigned a value to a numeric field (in Sharepoint for example) you cannot delete this value or update it to null/blank
This is a basic requirement. Why so long to fix!! Unable to Patch a null person on an SP list.
One way to go around this is to change the field type to Straight Line text in the sharepoint list and then change the text format to TextFormat.Number in Powerapps. works for me
This is definitly a requirment for CDS. I know it is available in SQL now but this needs to be in CDS.