fix count

Author: mtrezza

spec/RestQuery.spec.js

@@ -229,6 +229,15 @@ describe('rest query', () => {
     expect(results.length).toBe(0);
   });
 
+  it('count internal field that has no database column', async () => {
+    const user = new Parse.User();
+    user.setUsername('user1');
+    user.setPassword('password');
+    await user.signUp();
+    const count = await new Parse.Query(Parse.User).exists('_tombstone').count({ useMasterKey: true });
+    expect(count).toBe(0);
+  });
+
   it('query protected field', async () => {
     const user = new Parse.User();
     user.setUsername('username1');

src/Adapters/Storage/Postgres/PostgresStorageAdapter.js

@@ -2191,7 +2191,10 @@ export class PostgresStorageAdapter implements StorageAdapter {
         }
       })
       .catch(error => {
-        if (error.code !== PostgresRelationDoesNotExistError) {
+        if (
+          error.code !== PostgresRelationDoesNotExistError &&
+          error.code !== PostgresMissingColumnError
+        ) {
           throw error;
         }
         return 0;