Texture missing source when created by dragging and dropping to material (master based snapshot)

Tested with the latest master based snapshot 3.9, build number 410

Steps to reproduce:

• Create a 3D project
• Add some image file to project in Assets view
• Open Material Editor
• Drag and drop image file from Assets to Diffuse map in Material Editor
• -> Texture is created and applied to material but preview image of material is not changed to show the texture
• -> In Code view Texture component's source seems to be empty:
• Texture { id: texture1 source: "" }