The bug
In creative mode, right clicking with a single empty map will replace it in your hotbar with a map, while right-clicking with multiple empty maps (2-64) will not use up any empty maps and will create a map in a different location in your inventory.
Linked issues
Attachments
Comments 18
Confirmed for 1.7.9 and 14w17a
Confirmed for 1.8.7 and 1.10.2

Confirmed in 1.12.2
Confirmed for 1.13.1.

Confirmed for 19w03b

Confirmed for 19w03c
WAI

Comfirmed for 19w04a

Confirmed for 19w04b and 19w05a
Confirmed.