Win 7 64
Blender 2.8 26d5a3625ed, 2018-11-29 15:57
If you have two objects in pose mode, the [Shift+I / CTRL+Shift+C] commands to add IK / Constraints, will only give the option to add constraint to Active Bone, despite only one bone (in total) being selected.
This file contains two objects, one bone each. They're both in pose mode and only one bone is selected.
Press Shift+I , or Ctrl+Shift+C, to try to add a constraint, with a new empty object.