For non-official builds, Installer had no logo. This led to a window
sizing bug which is not seen in the official builds (both nightlies and
releases) as they both use the Haiku logo there.
Use Walter as a placeholder logo in that case. The png is generated from
the wonderbrush file in the separate artwork repo.
Change-Id: Iea361d7ac0fd2bdb147318632ff198c86c4b89c2
Reviewed-on: https://review.haiku-os.org/c/haiku/+/2180
Reviewed-by: waddlesplash <waddlesplash@gmail.com>
