Color output got broken - Use of Nil in string context in method split-color

Steps to reproduce:

$ SP6_FORMAT_COLOR=1 tomty streams-ranges-different-length
[repository] :: index updated from file:///root/repo/api/v1/index
[streams-ranges-different-length] ::
[streams-ranges-different-length] ::   foo
[streams-ranges-different-length] ::       2
[streams-ranges-different-length] ::       4
[streams-ranges-different-length] ::       6
[streams-ranges-different-length] ::       8
[streams-ranges-different-length] ::   bar
[streams-ranges-different-length] ::
[streams-ranges-different-length] ::   foo
[streams-ranges-different-length] ::       1
[streams-ranges-different-length] ::       3
[streams-ranges-different-length] ::   bar
[streams-ranges-different-length] ::
[streams-ranges-different-length] ::   foo
[streams-ranges-different-length] ::       0
[streams-ranges-different-length] ::       0
[streams-ranges-different-length] ::       0
[streams-ranges-different-length] ::   bar
[streams-ranges-different-length] ::
[task check] stdout match (r) <(\d+)> True
[task check] layer: 1 {2}
[task check] layer: 2 {4}
[task check] layer: 3 {6}
[task check] layer: 4 {8}
Use of Nil in string context
  in method split-colors at /opt/rakudo-pkg/share/perl6/site/sources/643E6756C59016E087C822EACCDE8DEA1C3A7197 (Colorizable) line 418
[task check]
[task check] layer: 1 {1}
[task check] layer: 2 {3}
Use of Nil in string context
  in method split-colors at /opt/rakudo-pkg/share/perl6/site/sources/643E6756C59016E087C822EACCDE8DEA1C3A7197 (Colorizable) line 418
[task check]
[task check] layer: 1 {0}
[task check] layer: 2 {0}
[task check] layer: 3 {0}
Use of Nil in string context
  in method split-colors at /opt/rakudo-pkg/share/perl6/site/sources/643E6756C59016E087C822EACCDE8DEA1C3A7197 (Colorizable) line 418
[task check]