Objects not spawnable anymore (through clicking in Gazebo)

[fairlight1337]

Today I noticed that spawning objects from the Gazebo library doesn't work anymore. The objects show up on the Insert tab of the left-hand menu, but clicking on them results in an error message on the console:

Error [ModelDatabase.cc:407] Unable to download model[model://ltfnp_models/models/buttermilk/ReineButterMilch.dae]
Error [SystemPaths.cc:367] File or path does not exist[""]
Error [Visual.cc:2133] No mesh specified

Curiously, the same thing works when spawning the object through the ROS service (/gazebo/spawn_urdf_model). In the call to the service, the contents of the URDF file are sent as a string, but the reference to the .dae file is the same.