Incorrect summary in model-check tabs

[chrispcampbell]

In a recent change (see PR #551) I refactored the code that adds up the number of scenarios or datasets that have differences. It looks like I introduced a bug because the tabs in the model-check summary page are now showing the total number of rows rather than the number of rows with significant differences:

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The problematic code is here:

[chrispcampbell]

The code was changed accidentally to calculate the total number of rows. It needs to be changed back similar to how it was before, where we subtract the "without diffs" count from the total number of rows.

[chrispcampbell]

The tabs now show the correct summaries in the case where there are no differences:

And the correct summaries when there are some differences: