Brave crashes if alert is called without a message

[bridiver]

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Yes

Describe the issue you encountered:
from https://hackerone.com/reports/175850
<script>alert()</script> will crash brave on toString

Expected behavior:

• Platform (Win7, 8, 10? macOS? Linux distro?):
  All
• Brave Version:
  master

[luixxiul]

Any page to test this?

[alexwykoff]

@luixxiul It's pretty easy to write a local file and open it. The behavior is the the same.

[willy-b]

You can also use paste a data URL right into the URL bar: data:text/html,<script>alert()</script>

[willy-b]

BTW, this is still an issue if you pass a title which is a number, e.g.:
data:text/html,<script>alert(1, 1)</script> will crash Brave.

EDIT: rolled this into PR #4891