fix type

Author: max-ostapenko

definitions/output/crawl/parsed_css.js

@@ -17,7 +17,7 @@ WHERE date = '${constants.currentMonth}'
 `).query(ctx => `
 SELECT
   * EXCEPT(css),
-  NULL AS css_backup,
+  CAST(NULL AS STRING) AS css_backup,
   SAFE.PARSE_JSON(css, wide_number_mode=>'round') AS css
 FROM ${ctx.ref('crawl_staging', 'parsed_css')}
 WHERE date = '${constants.currentMonth}'
@@ -31,7 +31,7 @@ WHERE date = '${constants.currentMonth}'
 INSERT INTO ${ctx.self()}
 SELECT
   * EXCEPT(css),
-  NULL AS css_backup,
+  CAST(NULL AS STRING) AS css_backup,
   SAFE.PARSE_JSON(css, wide_number_mode=>'round') AS css
 FROM ${ctx.ref('crawl_staging', 'parsed_css')}
 WHERE date = '${constants.currentMonth}'