UtBS S9: Avoid 'punishing' the player for saving the rebels (#6362)

* Avoid 'punishing' the player for avoiding bloodshed by giving rebels zero upkeep costs for the scenario upon reuniting with Kaleh's side.

Resolves #6229.

Co-authored-by: Descacharrado <Luis_koopa@hotmail.com>
(cherry picked from commit 594f0cd293)

data/campaigns/Under_the_Burning_Suns/scenarios/09_Blood_is_Thicker_Than_Water.cfg

@@ -2345,6 +2345,14 @@
                 side=3
             [/filter]
             side=1
+            # If the player kept as many of the rebels alive as possible it's possible for their income to become negative. Give the unit no upkeep cost to compensate.
+            # Note that having loyal upkeep is not the same as having the loyal trait, no loyal overlay will be displayed.
+            [object]
+                duration=scenario
+                [effect]
+                    apply_to=loyal
+                [/effect]
+            [/object]
         [/modify_unit]
         [redraw]
             clear_shroud=yes