000050: Cannot add a field to a joined table.
Description
If a layer has a table joined to it, adding or removing fields is not allowed. You must remove all joins prior to adding or removing a field.
Solution
Run the Remove Join tool on the layer.
If a layer has a table joined to it, adding or removing fields is not allowed. You must remove all joins prior to adding or removing a field.
Run the Remove Join tool on the layer.