## Bug description

The following filter fails with a 500 internal error.

![2021-02-04_12-07](https://user-images.githubusercontent.com/148820/106877644-a9f4ce80-66e1-11eb-8320-87bb213bdde2.png)


## Expected behavior

Error is shown to user about invalid regular expression.

Note no errors shown on the page as well.

## How to reproduce

1. Go to events
2. Add filter "Current URL matches regular expression ?*"
3. See infinite loading screen / error

## Environment

- [x] PostHog Cloud
- [x] self-hosted PostHog, version/commit: _please provide_

## Additional context

Note this can also happen when filtering by events.

#### *Thank you* for your bug report – we love squashing them!

ee/clickhouse/models/property.py
from typing import Any, Dict, List, Optional, Tuple
from django.conf import settings
from django.utils import timezone
from ee.clickhouse.client import sync_execute
from ee.clickhouse.models.cohort import format_filter_query
from ee.clickhouse.models.util import is_int, is_json
from ee.clickhouse.sql.events import SELECT_PROP_VALUES_SQL, SELECT_PROP_VALUES_SQL_WITH_FILTER
from ee.clickhouse.sql.person import GET_DISTINCT_IDS_BY_PROPERTY_SQL
from posthog.models.cohort import Cohort
from posthog.models.property import Property
from posthog.models.team import Team
from posthog.utils import relative_date_parse
def parse_prop_clauses(
    filters: List[Property],
    team_id: Optional[int],
    prepend: str = "global",
    table_name: str = "",
    allow_denormalized_props: bool = False,
) -> Tuple[str, Dict]:
    final = []
    params: Dict[str, Any] = {}
    if team_id is not None:
        params["team_id"] = team_id
    if table_name != "":
        table_name += "."