fixed bug for index scan when index column is not nullable. (#3012)

* fixed nullable error

* tck fmt

src/storage/index/LookupBaseProcessor-inl.h

@@ -196,7 +196,7 @@ StatusOr<StoragePlan<IndexID>> LookupBaseProcessor<REQ, RESP>::buildPlan(
     auto fields = indexItem->get_fields();
 
     for (const auto& col : fields) {
-      if (!hasNullableCol && col.get_nullable()) {
+      if (!hasNullableCol && col.nullable_ref().value_or(false)) {
         hasNullableCol = true;
         break;
       }

tests/tck/features/insert/Insert.feature

@@ -466,6 +466,8 @@ Feature: Insert string vid of vertex and edge
       """
       CREATE TAG student(name string NOT NULL, age int);
       CREATE TAG course(name fixed_string(5) NOT NULL, introduce string DEFAULT NULL);
+      CREATE TAG INDEX student_i ON student(name(30), age);
+      CREATE TAG INDEX course_i ON course(name, introduce(30));
       """
     # test insert with fixed_string
     When try to execute query:
@@ -491,11 +493,6 @@ Feature: Insert string vid of vertex and edge
       INSERT VERTEX student(name, age) VALUES "Tom":(NULL, 12)
       """
     Then a ExecutionError should be raised at runtime: Storage Error: The not null field cannot be null.
-    When executing query:
-      """
-      INSERT VERTEX student(name, age) VALUES "Tom":(NULL, 12)
-      """
-    Then a ExecutionError should be raised at runtime: Storage Error: The not null field cannot be null.
     # out of fixed_string's size
     When executing query:
       """
@@ -518,4 +515,20 @@ Feature: Insert string vid of vertex and edge
     Then the result should be, in any order:
       | VertexID | student.name | student.age |
       | ''       | 'Tom'        | 12          |
+    # check result
+    When executing query:
+      """
+      LOOKUP on course YIELD course.name, course.introduce
+      """
+    Then the result should be, in any order:
+      | VertexID  | course.name | course.introduce |
+      | 'English' | 'Engli'     | NULL             |
+      | 'Math'    | 'Math'      | NULL             |
+    When executing query:
+      """
+      LOOKUP ON student YIELD student.name, student.age
+      """
+    Then the result should be, in any order:
+      | VertexID | student.name | student.age |
+      | ''       | 'Tom'        | 12          |
     Then drop the used space