Test failure: TextLens.range gets "" if invalid range

Built with GHC 8.4:
```
Failures:

test/Spec.hs:136:
1) TextLens.range gets "" if invalid range
uncaught exception: ErrorCall (Data.Text.Array.new: size overflow
CallStack (from HasCallStack):
error, called at libraries/text/Data/Text/Array.hs:132:20 in text-1.2.3.0:Data.Text.Array)

Randomized with seed 856691866

Finished in 0.0017 seconds
```

Start with test/Spec.hs at line 136 and run the failing test under GHC 8.4 to reproduce the TextLens.range invalid-range failure. Trace the range handling and confirm that an invalid range returns an empty string without raising the Data.Text.Array size-overflow exception.

Written by the indexing model from the issue text.