If you right click on unselected texture on material browser, most items in context menu are disabled

Create 3D project and make sure material browser has at least two textures and one material

• Select a texture with left click
• Right click on selected texture
  -> Context menu opens and menu items are enabled as expected

• Right click on unselected texture
  -> The texture is selected but the menu contents are mostly disabled as if you'd clicked on empty part of the texture area.