Remove non null assertion on oldSourceFile.resolvedModules (#38984)
Remove non null assertion on oldSourceFile.resolvedModules (#38984)

Fixes #37938
RyanCavanaugh/TypeScript,weswigham/TypeScript,SaschaNaz/TypeScript,microsoft/TypeScript,kpreisser/TypeScript,microsoft/TypeScript,weswigham/TypeScript,kitsonk/TypeScript,kitsonk/TypeScript,weswigham/TypeScript,Microsoft/TypeScript,kpreisser/TypeScript,RyanCavanaugh/TypeScript,RyanCavanaugh/TypeScript,kitsonk/TypeScript,Microsoft/TypeScript,SaschaNaz/TypeScript,Microsoft/TypeScript,SaschaNaz/TypeScript,kpreisser/TypeScript,microsoft/TypeScript,SaschaNaz/TypeScript