id,node_id,number,title,user,state,locked,assignee,milestone,comments,created_at,updated_at,closed_at,author_association,pull_request,body,repo,type,active_lock_reason,performed_via_github_app,reactions,draft,state_reason
545407916,MDU6SXNzdWU1NDU0MDc5MTY=,73,upsert_all() throws issue when upserting to empty table,82988,closed,0,,,6,2020-01-05T11:58:57Z,2020-01-31T14:21:09Z,2020-01-05T17:20:18Z,NONE,,"If I try to add a list of `dict`s to an empty table using `upsert_all`, I get an error:

```python
import sqlite3
from sqlite_utils import Database
import pandas as pd

conx = sqlite3.connect(':memory')
cx = conx.cursor()
cx.executescript('CREATE TABLE ""test"" (""Col1"" TEXT);')

q=""SELECT * FROM test;""
pd.read_sql(q, conx) #shows empty table

db = Database(conx)
db['test'].upsert_all([{'Col1':'a'},{'Col1':'b'}])

---------------------------------------------------------------------------
TypeError                                 Traceback (most recent call last)
<ipython-input-74-8c26d93d7587> in <module>
      1 db = Database(conx)
----> 2 db['test'].upsert_all([{'Col1':'a'},{'Col1':'b'}])

/usr/local/lib/python3.7/site-packages/sqlite_utils/db.py in upsert_all(self, records, pk, foreign_keys, column_order, not_null, defaults, batch_size, hash_id, alter, extracts)
   1157             alter=alter,
   1158             extracts=extracts,
-> 1159             upsert=True,
   1160         )
   1161 

/usr/local/lib/python3.7/site-packages/sqlite_utils/db.py in insert_all(self, records, pk, foreign_keys, column_order, not_null, defaults, batch_size, hash_id, alter, ignore, replace, extracts, upsert)
   1040                     sql = ""INSERT OR IGNORE INTO [{table}]({pks}) VALUES({pk_placeholders});"".format(
   1041                         table=self.name,
-> 1042                         pks="", "".join([""[{}]"".format(p) for p in pks]),
   1043                         pk_placeholders="", "".join([""?"" for p in pks]),
   1044                     )

TypeError: 'NoneType' object is not iterable

```

A hacky workaround in use is:

```python
try:
  db['test'].upsert_all([{'Col1':'a'},{'Col1':'b'}])
except:
  db['test'].insert_all([{'Col1':'a'},{'Col1':'b'}])
```",140912432,issue,,,"{""url"": ""https://api.github.com/repos/simonw/sqlite-utils/issues/73/reactions"", ""total_count"": 0, ""+1"": 0, ""-1"": 0, ""laugh"": 0, ""hooray"": 0, ""confused"": 0, ""heart"": 0, ""rocket"": 0, ""eyes"": 0}",,completed