Incorrect "Character Suite mismatch" message in copy_pages

[srjfoo]

Discovered by MWS.

If the destination project in copy_pages has all three Extended European Latin character suites, but the source project only has B and C, you get the following warning:

Character Suite mismatch

The following character suites are in the source project but not in the destination project. Ensure the copied pages do not use these or adjust the destination project character suites accordingly.

    basic-latin
    extended-european-latin-c

I've tested it with several other combinations, but haven't so far gotten a similar erroneous warning. Test projects to verify:

Destination: projectID62151244d8b17
Source project: projectID62145dc56ac7b