Merge pull request #2043 from metabase/fix-bigquery-null-values

Workaround BigQuery NULL value bug 

src/metabase/driver/bigquery.clj

@@ -183,7 +183,11 @@
      :cols    cols
      :rows    (for [^TableRow row (.getRows response)]
                 (for [[^TableCell cell, parser] (partition 2 (interleave (.getF row) parsers))]
-                  (parser (.getV cell))))}))
+                  (when-let [v (.getV cell)]
+                    ;; There is a weird error where everything that *should* be NULL comes back as an Object. See https://jira.talendforge.org/browse/TBD-1592
+                    ;; Everything else comes back as a String luckily so we can proceed normally.
+                    (when-not (= (class v) Object)
+                      (parser v)))))}))
 
 (defn- process-native* [database query-string]
   (post-process-native (execute-query database query-string)))