refactor(datasource/helm): Enable strict null checks (#14040)

lib/datasource/helm/index.ts

@@ -89,6 +89,11 @@ export class HelmDatasource extends Datasource {
     lookupName,
     registryUrl: helmRepository,
   }: GetReleasesConfig): Promise<ReleaseResult | null> {
+    // istanbul ignore if
+    if (!helmRepository) {
+      return null;
+    }
+
     const repositoryData = await this.getRepositoryData(helmRepository);
     if (!repositoryData) {
       logger.debug(`Couldn't get index.yaml file from ${helmRepository}`);

tsconfig.strict.json

@@ -107,8 +107,6 @@
     "lib/datasource/go/types.ts",
     "lib/datasource/golang-version/index.ts",
     "lib/datasource/gradle-version/index.ts",
-    "lib/datasource/helm/common.ts",
-    "lib/datasource/helm/index.ts",
     "lib/datasource/index.ts",
     "lib/datasource/jenkins-plugins/index.ts",
     "lib/datasource/npm/get.ts",