feat: 지원서 응답에 관심 분야가 null일 경우 빈 리스트로 처리하도록 수정

Author: fivedragon5

src/main/java/org/ject/support/domain/admin/dto/SubmittedApplyResponse.java

@@ -44,7 +44,9 @@ public static SubmittedApplyResponse from(Apply apply,
                 Optional.ofNullable(apply.getMember().getExperiencePeriod())
                         .map(ExperiencePeriod::getDescription)
                         .orElse(""),
-                new ArrayList<>(apply.getMember().getInterestedDomains()),
+                new ArrayList<>(Optional.ofNullable(apply.getMember().getInterestedDomains())
+                        .orElse(List.of())
+                ),
                 Optional.ofNullable(apply.getApplicationForm())
                         .map(ApplicationForm::getPortfolios)
                         .map(portfolioList -> !portfolioList.isEmpty())