'master' branch does not clean build - errors "TS2538: Type 'null' cannot be used as an index type."

[Mike Whittaker]

Linux Ubuntu 18.x, latest node.js, npm
branch master
SHA: deff711

eg

 /ModernDeck/src/DesktopConfigParser.ts
./src/DesktopConfigParser.ts 26:29-35
[tsl] ERROR in ..../ModernDeck/src/DesktopConfigParser.ts(26,30)
      TS2538: Type 'null' cannot be used as an index type.
 @ ./src/AppController.ts 14:0-52 50:8-19
 @ ./src/Boot/Items/AppFunctions.ts 7:0-54 9:4-19
 @ ./src/Boot/Stages/Core.ts 47:0-57 74:57-73
 @ ./src/Boot/Boot.ts 48:0-42 60:37-46

[dangered wolf]

Fixed