When something is null in the database, it won't exist in the JSON response we get from Maximo because it's set to drop nulls. In that scenario it is actually undefined. You typically want to use {!ds.item.field} to indicate that the field doesn't exist (could be null, undefined, etc.) or {ds.item.field} to indicate that it does exist.
You also don't want to check the woPlanTaskDetaildsSelected datasource because that is a JSON datasource that will have 1 and only 1 task loaded into it and it seems like you're trying to display observation in the data-list. You should just be using item.pointnum. Since you want to hide it when the pointnum exists (is something other than undefined, null, etc.), you should have hidden="{item.pointnum}".
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Steven Shull
IBM
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