A non-sink operator's results disappear on the frontend during execution

[Xiao-zhen-Liu]

#1292 introduced a logic to clear results for the result panel when a result update event from the backend does not contain the current operator. This was based on the assumption that only sink operators' results can be viewed. Since this assumption has changed, this logic will cause an intermediate operator's results that is currently being viewed to be cleared if other operator results in the workflow are updated.
Need to revisit this piece of code (lines 81 - 90 of result-table-frame.component.ts).