typescript-angular: Fix Cannot read property 'apiKey' of undefined

[EmmanuelRoux]

This fixes #9259 and may possibly fix #8980 and fix #8983

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[EmmanuelRoux]

@TiFu @taxpon @sebastianhaas @kenisteward @Vrolijkx @macjohnny @topce @akehir @petejohansonxo @amakhrov

[macjohnny]

Thanks for your contribution.
Since we also support okder typescript versions, please fix the issue without using the optional chaining operator.
https://github.com/OpenAPITools/openapi-generator/blob/60dcf8613f6b75b606757c4a991fe018ad10ee99/modules/openapi-generator/src/main/java/org/openapitools/codegen/languages/TypeScriptAngularClientCodegen.java#L288-302
https://www.typescriptlang.org/docs/handbook/release-notes/typescript-3-7.html

[macjohnny]

LGTM