Treat host as possibly undefined for base64encode/base64decode
Treat host as possibly undefined for base64encode/base64decode

Fixes: #24638

Microsoft/TypeScript,donaldpipowitch/TypeScript,microsoft/TypeScript,nojvek/TypeScript,Microsoft/TypeScript,minestarks/TypeScript,alexeagle/TypeScript,kpreisser/TypeScript,basarat/TypeScript,basarat/TypeScript,basarat/TypeScript,SaschaNaz/TypeScript,weswigham/TypeScript,RyanCavanaugh/TypeScript,donaldpipowitch/TypeScript,minestarks/TypeScript,alexeagle/TypeScript,weswigham/TypeScript,weswigham/TypeScript,nojvek/TypeScript,SaschaNaz/TypeScript,basarat/TypeScript,kpreisser/TypeScript,RyanCavanaugh/TypeScript,alexeagle/TypeScript,minestarks/TypeScript,SaschaNaz/TypeScript,kitsonk/TypeScript,kitsonk/TypeScript,kitsonk/TypeScript,donaldpipowitch/TypeScript,RyanCavanaugh/TypeScript,Microsoft/TypeScript,kpreisser/TypeScript,nojvek/TypeScript,microsoft/TypeScript,SaschaNaz/TypeScript,donaldpipowitch/TypeScript,microsoft/TypeScript,nojvek/TypeScript