[REG: 3.1 -> 3.2] Cannot import assets with drag and drop when project has no existing assets

Steps to reproduce:

• Create a new project
• Open Assets view
• Try dragging and dropping 2D or 3D assets to Assets view -> Cannot do the drop, "not allowed" icon is shown
• Add one 2D asset by clicking + in assets
• -> now adding more assets with drag and drop is allowed