GUI: incorrect damage distribution dialog for big font settings

**Description**
When I assign damage to 2 creatures with Fire Covenant, the "Choose" button is only available for X-1 damage to the first creature, resulting in 1 damage to the 2nd creature.

**Example 1**
Creature 1: Kambal, Consul of Allocation
Creature 2: High Priest of Penance with Dancing Sword equipped

Pay 5 life
Result: can only give 4 damage to Kambul and 1 to the Priest, button is greyed out for all other options.

**Example 2**
Creature 1: High Priest of Penance with Dancing Sword equipped
Creature 2: Kambal, Consul of Allocation

Pay 10 life
Result: can only give 9 damage to the Priest and 1 to Kambul, button is greyed out for all other options.

**Screenshot**

Note how the Choose button is greyed out, even though I should be able to give 8 out of 10 damage to the first creature, if I wished.