Affect of Shrinking Database before Transaction log backup
Your maintenance plan should not contain any shrink tasks anyway. These cause fragmentation by moving pages around the file and likely the database will just need to grow back to its original size shortly anyway.

But this isn't causing your error. 


  BACKUP LOG cannot be performed because there is no current database
  backup.


The transaction logs would need to be restored after a compatible backup has been restored. This is telling you that there is no such backup as one has never been taken since the database has been in full or bulk logged recovery mode.

It doesn't look like step 1 was run successfully for that database, or possibly someone temporarily changed the recovery mode for that database to simple and broke the log chain so you must take another full backup.