Don't populate IdentifierCollection errors with empty nested arrays #740

Job	Run time
cs-stan / Coding Standard & Static Analysis	30s
testsuite / testsuite-linux (8.2, highest, false)	38s
testsuite / testsuite-linux (8.1, highest, false)	36s
testsuite / testsuite-linux (8.4, highest, false)	1m 26s
testsuite / testsuite-linux (8.1, lowest, false)	32s
testsuite / testsuite-linux (8.3, highest, false)	37s
	4m 19s

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