Fix bug: return `undefined`, not `false`
Fix bug: return `undefined`, not `false`

donaldpipowitch/TypeScript,erikmcc/TypeScript,DLehenbauer/TypeScript,DLehenbauer/TypeScript,donaldpipowitch/TypeScript,RyanCavanaugh/TypeScript,Microsoft/TypeScript,chuckjaz/TypeScript,SaschaNaz/TypeScript,microsoft/TypeScript,synaptek/TypeScript,TukekeSoft/TypeScript,erikmcc/TypeScript,SaschaNaz/TypeScript,mihailik/TypeScript,jwbay/TypeScript,erikmcc/TypeScript,SaschaNaz/TypeScript,basarat/TypeScript,weswigham/TypeScript,jwbay/TypeScript,nojvek/TypeScript,chuckjaz/TypeScript,microsoft/TypeScript,basarat/TypeScript,donaldpipowitch/TypeScript,DLehenbauer/TypeScript,kpreisser/TypeScript,TukekeSoft/TypeScript,kitsonk/TypeScript,weswigham/TypeScript,minestarks/TypeScript,synaptek/TypeScript,DLehenbauer/TypeScript,jwbay/TypeScript,mihailik/TypeScript,synaptek/TypeScript,nojvek/TypeScript,mihailik/TypeScript,Eyas/TypeScript,mihailik/TypeScript,donaldpipowitch/TypeScript,kitsonk/TypeScript,chuckjaz/TypeScript,SaschaNaz/TypeScript,microsoft/TypeScript,RyanCavanaugh/TypeScript,nojvek/TypeScript,alexeagle/TypeScript,synaptek/TypeScript,Eyas/TypeScript,basarat/TypeScript,minestarks/TypeScript,erikmcc/TypeScript,alexeagle/TypeScript,RyanCavanaugh/TypeScript,kitsonk/TypeScript,TukekeSoft/TypeScript,kpreisser/TypeScript,Eyas/TypeScript,jwbay/TypeScript,basarat/TypeScript,Microsoft/TypeScript,kpreisser/TypeScript,nojvek/TypeScript,minestarks/TypeScript,weswigham/TypeScript,alexeagle/TypeScript,Microsoft/TypeScript,chuckjaz/TypeScript,Eyas/TypeScript