`process_cov` throws `BoundsError: attempt to access 8-codeunit String at index [1:9]`

BoundsError: attempt to access 8-codeunit String at index [1:9]
Stacktrace:
  [1] checkbounds
    @ ./strings/basic.jl:216 [inlined]
  [2] getindex
    @ ./strings/string.jl:265 [inlined]
  [3] process_cov(filename::String, folder::String)
    @ CoverageTools ~/.julia/packages/CoverageTools/JSYpL/src/CoverageTools.jl:133
  [4] process_file(filename::String, folder::String)
    @ CoverageTools ~/.julia/packages/CoverageTools/JSYpL/src/CoverageTools.jl:232
  [5] process_folder(folder::String)
    @ CoverageTools ~/.julia/packages/CoverageTools/JSYpL/src/CoverageTools.jl:258
  [6] process_folder(folder::String) (repeats 2 times)
    @ CoverageTools ~/.julia/packages/CoverageTools/JSYpL/src/CoverageTools.jl:264
  [7] (::var"#3#4")()
    @ Main ~/test_retestitems.jl:39
  [8] with_logstate(f::Function, logstate::Any)
    @ Base.CoreLogging ./logging.jl:511
  [9] with_logger(f::Function, logger::Logging.ConsoleLogger)
    @ Base.CoreLogging ./logging.jl:623
 [10] top-level scope
    @ ~/script.jl:38

https://github.com/JuliaCI/CoverageTools.jl/blob/9d8fba371f4c65a7e9ca3bdaae753a52bcb22218/src/CoverageTools.jl#L133

Where ~/script.jl:38 looks like:

    Logging.with_logger(Logging.ConsoleLogger(stderr, Logging.Warn)) do
        src_coverage = Coverage.process_folder("src")
        LCOV.writefile("lcov.info", src_coverage)
    end

Start at src/CoverageTools.jl:133 in process_cov, then trace the call from process_folder shown in the report. Reproduce with the provided Logging.with_logger and Coverage.process_folder("src") example; done means the reported BoundsError no longer occurs while processing the coverage folder.