Are you using XSLT 1.0 or 2.0?
XSLT 1.0 does not have a "string array" type.
XSLT 2.0 has "sequences of strings" - is this what you are referring to?
Which XSLT processor are you using?
What does the extension function scripts:GetInspectionTime do?
The evidence suggests that your variable _arrInspectionTimes contains an empty sequence (or if it's 1.0, and empty node-set), and if you believe that isn't the case, then you need to convince your readers why.
Author, XSLT 2.0 and XPath 2.0 Programmer\'s Reference