bulk upload handles invalid byte sequences

- sometimes csv is not exported as utf8 therefore invalid byte sequences
  are removed

app/services/bulk_upload/lettings/csv_parser.rb

@@ -52,6 +52,7 @@ private
 
     @normalised_string = File.read(path, encoding: "bom|utf-8")
     @normalised_string.gsub!("\r\n", "\n")
+    @normalised_string.scrub!("")
 
     @normalised_string
   end

spec/services/bulk_upload/lettings/csv_parser_spec.rb

@@ -52,4 +52,21 @@ RSpec.describe BulkUpload::Lettings::CsvParser do
       expect(service.row_parsers[0].field_12).to eql(log.age1)
     end
   end
+
+  context "when an invalid byte sequence" do
+    let(:file) { Tempfile.new }
+    let(:path) { file.path }
+    let(:log) { build(:lettings_log, :completed) }
+    let(:invalid_sequence) { "\x81" }
+
+    before do
+      file.write(invalid_sequence)
+      file.write(BulkUpload::LogToCsv.new(log:, col_offset: 0).to_csv_row)
+      file.close
+    end
+
+    it "parses csv correctly" do
+      expect(service.row_parsers[0].field_12).to eql(log.age1)
+    end
+  end
 end