HOTFIX: tile dynamodb isEmpty filter not respecting NULL values (#1249)

## Problem

Our current isEmpty filter for Tiles v1 only checks for empty string and
missing values (undefined). However, when manually updating rows on the
Tile frontend, it sets the empty cells to NULL which is not satisfied by
our filter.

## Solution

Add NULL check to isEmpty filter

Author: pregnantboy

packages/backend/src/models/tiles/dynamodb/__tests__/table-row/functions.itest.ts

@@ -258,6 +258,34 @@ describe('dynamodb table row functions', () => {
       expect(rows8.length).toEqual(1000)
     })
 
+    it('empty filter should work with empty string, null and undefined', async () => {
+      const dataArray: any[] = []
+      ;['', null, 123, 'abc'].forEach((value, index) => {
+        dataArray.push({
+          a: `${index}`,
+          b: value,
+        })
+      })
+      dataArray.push({
+        a: `undefined value`,
+      })
+      await createTableRows({ tableId: dummyTable.id, dataArray })
+
+      // Empty
+      const { rows } = await getTableRows({
+        tableId: dummyTable.id,
+        columnIds: ['a', 'b'],
+        filters: [
+          {
+            columnId: 'b',
+            operator: TableRowFilterOperator.IsEmpty,
+            value: '',
+          },
+        ],
+      })
+      expect(rows.length).toEqual(3)
+    })
+
     it('should get relevant rows based on composite filters', async () => {
       const dataArray = []
       for (let i = 0; i < 1000; i++) {

packages/backend/src/models/tiles/dynamodb/table-row/functions.ts

@@ -121,7 +121,10 @@ const addFiltersToQuery = (
 ): void => {
   if (filters?.length) {
     query.where(
-      ({ data }, { eq, begins, contains, gt, gte, lt, lte, notExists }) => {
+      (
+        { data },
+        { eq, begins, contains, gt, gte, lt, lte, notExists, type },
+      ) => {
         const whereExpressions: string[] = []
         for (const filter of filters) {
           const { columnId, operator, value } = filter
@@ -150,7 +153,9 @@ const addFiltersToQuery = (
               break
             case TableRowFilterOperator.IsEmpty:
               whereExpressions.push(
-                `(${eq(data[columnId], '')} OR ${notExists(data[columnId])})`,
+                `(${eq(data[columnId], '')} OR ${notExists(
+                  data[columnId],
+                )} OR ${type(data[columnId], 'NULL')})`,
               )
               break
           }