Missing asset placeholder on project list when project avatar is not specified

[bkraul]

• Gitea version (or commit ref): 3fd1883
• Git version: 1.9.0+dev-312-g8a343dda3
• Operating system: docker (Ubuntu 18.04 LTS host)
• Database (use [x]):
  • PostgreSQL
  • MySQL
  • MSSQL
  • SQLite
• Can you reproduce the bug at https://try.gitea.io:
  • Yes (provide example URL): https://try.gitea.io/Arrow
  • No
  • Not relevant
• Log gist:

Description

When a project avatar is not specified, the project list (both in explore and organizational listings) shows a "hole" placeholder. It would probably be better to either have a default project avatar, or to not even show the place holder.

Screenshots

[lunny]

will be fixed by #7087