Allow undefined commit date

Author: aegilops

src/types.ts

@@ -122,7 +122,7 @@ export interface DependencyReviewPackageChange {
 }
 
 export interface BranchDependencyDiff {
-  latestCommitDate: string;
+  latestCommitDate?: string;
   base: string; // base branch
   head: string; // head branch
   retrievedAt: string;