Fix queries over ill-formatted geospatial data

[ironage]

We had a report that running a query over objects that didn't have the expected type property set to 'Point' would throw an exception. This is disruptive and not typical behaviour for queries. Instead, we should ignore those objects and not include them in the result set.

☑️ ToDos

• 📝 Changelog update
• 🚦 Tests (or not relevant)
• C-API, if public C++ API changed.

[coveralls-official]

Pull Request Test Coverage Report for Build james.stone_372

• 33 of 33 (100.0%) changed or added relevant lines in 2 files are covered.
• 25 unchanged lines in 8 files lost coverage.
• Overall coverage increased (+0.01%) to 91.184%

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Files with Coverage Reduction	New Missed Lines	%
src/realm/index_string.hpp	1	82.86%
src/realm/array_string.cpp	2	87.78%
src/realm/sync/noinst/client_impl_base.cpp	2	85.37%
src/realm/util/file.cpp	2	81.57%
test/test_thread.cpp	3	66.67%
test/util/compare_groups.cpp	3	54.12%
src/realm/index_string.cpp	6	87.76%
src/realm/sync/noinst/server/server.cpp	6	75.56%

Totals
Change from base Build 1696:	0.01%
Covered Lines:	232372
Relevant Lines:	254839

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💛 - Coveralls

[nirinchev]

I think this change makes sense.