Fix ActiveContext pause control check

What does this MR do and why?

Currently, the ActiveContext.pause? check returns false if ::ActiveContext.indexing? is false. I think this is an inverse condition. It should be:

ActiveContext indexing enabled?	Pause?
NO	YES, and immediately return true
YES	NO, and proceed to next pause-control checks

References

MR introducing pause control: Active Context: Add pause_control (!198912 - merged)

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