Fix various minor issues (FAForever#3598)

* Reduce muzzle velocity of Rhino

* Prevent gifting insignificant units

* Destroy weapon trashbags when the unit is killed

* Add check if unit has OnGiven (dummy units do not)

* Change callback logic

Introduced an empty callback and prevent non-existing callbacks
from generating errors - they cause spew messages instead

* Fix Cybran build sparks visibility

effects/emitters/build_sparks_blue_01_emit.bp

@@ -13,7 +13,7 @@ EmitterBlueprint {
     LODCutoff = 100.00,
     EmitIfVisible = true,
     CatchupEmit = true,
-    CreateIfVisible = true,
+    CreateIfVisible = false,
     SnapToWaterline = false,
     OnlyEmitOnWater = false,
     TextureStripcount = 1.00,

lua/SimCallbacks.lua

@@ -50,7 +50,7 @@ function DoCallback(name, data, units)
     if fn then
         fn(data, units)
     else
-        error('No callback named ' .. repr(name))
+        SPEW('No callback named: ' .. repr(name))
     end
 end
 
@@ -74,6 +74,10 @@ local function SecureUnits(units)
     return secure
 end
 
+--- Empty callback for ui mods to communicate
+Callbacks.EmptyCallback = function(data, units)
+end
+
 Callbacks.AutoOvercharge = function(data, units)
     for _, u in units or {} do
         if IsEntity(u) and OkayToMessWithArmy(u.Army) and u.SetAutoOvercharge then

lua/SimUtils.lua

@@ -68,6 +68,10 @@ function TransferUnitsOwnership(units, ToArmyIndex, captured)
         shareUpgrades = true
     end
 
+    -- do not gift insignificant units
+    units = EntityCategoryFilterDown(categories.ALLUNITS - categories.INSIGNIFICANTUNIT, units)
+
+    -- gift most valuable units first
     table.sort(units, function (a, b) return a:GetBlueprint().Economy.BuildCostMass > b:GetBlueprint().Economy.BuildCostMass end)
 
     local newUnits = {}
@@ -229,7 +233,9 @@ function TransferUnitsOwnership(units, ToArmyIndex, captured)
 
         unit.IsBeingTransferred = false
 
-        v:OnGiven(unit)
+        if v.OnGiven then 
+            v:OnGiven(unit)
+        end
     end
 
     if not captured then

lua/sim/Unit.lua

@@ -1195,6 +1195,11 @@ Unit = Class(moho.unit_methods) {
         local layer = self.Layer
         self.Dead = true
 
+        -- destroy all weapon effects
+        for k = 1, self.WeaponCount do 
+            self.WeaponInstances[k].Trash:Destroy();
+        end
+
         -- Units killed while being invisible because they're teleporting should show when they're killed
         if self.TeleportFx_IsInvisible then
             self:ShowBone(0, true)

units/URL0202/URL0202_unit.bp

@@ -217,7 +217,7 @@ UnitBlueprint {
             MaxRadius = 24,
             MuzzleSalvoDelay = 0,
             MuzzleSalvoSize = 1,
-            MuzzleVelocity = 400,
+            MuzzleVelocity = 100,
             ProjectilesPerOnFire = 1,
             ProjectileId = '/projectiles/CDFLaserHeavy02/CDFLaserHeavy02_proj.bp',
             RackBones = {