fix field_4 validation for bulk upload

- the null check was inverted by mistake

app/services/bulk_upload/lettings/row_parser.rb

@@ -140,7 +140,8 @@ class BulkUpload::Lettings::RowParser
   attribute :field_134, :integer
 
   validates :field_1, presence: true, inclusion: { in: (1..12).to_a }
-  validates :field_4, presence: { if: proc { [1, 3, 5, 7, 9, 11].include?(field_1) } }
+  validates :field_4, presence: { if: proc { [2, 4, 6, 8, 10, 12].include?(field_1) } }
+
   validates :field_96, presence: true
   validates :field_97, presence: true
   validates :field_98, presence: true

spec/services/bulk_upload/lettings/row_parser_spec.rb

@@ -13,7 +13,7 @@ RSpec.describe BulkUpload::Lettings::RowParser do
   let(:setup_section_params) do
     {
       bulk_upload:,
-      field_1: "1",
+      field_1: "2",
       field_111: owning_org.old_visible_id,
       field_113: managing_org.old_visible_id,
       field_96: now.day.to_s,
@@ -205,19 +205,19 @@ RSpec.describe BulkUpload::Lettings::RowParser do
     end
 
     describe "#field_4" do
-      context "when nullable permitted" do
+      context "when nullable not permitted" do
         let(:attributes) { { bulk_upload:, field_1: "2", field_4: nil } }
 
-        it "can be nulled" do
-          expect(parser.errors[:field_4]).to be_blank
+        it "cannot be nulled" do
+          expect(parser.errors[:field_4]).to be_present
         end
       end
 
-      context "when nullable not permitted" do
+      context "when nullable permitted" do
         let(:attributes) { { bulk_upload:, field_1: "1", field_4: nil } }
 
-        it "cannot be nulled" do
-          expect(parser.errors[:field_4]).to be_present
+        it "can be nulled" do
+          expect(parser.errors[:field_4]).to be_blank
         end
       end