Event prefix can be nil, if the event occurs on a non-spawned group with no # tag.

Moose Development/Moose/Functional/Spawn.lua

@@ -1595,12 +1595,14 @@ function SPAWN:_OnBirth( EventData )
   
   if SpawnGroup then
     local EventPrefix = self:_GetPrefixFromGroup( SpawnGroup )
+    if EventPrefix then -- EventPrefix can be nil if no # is found, which means, no spawnable group!
   		self:T( { "Birth Event:", EventPrefix, self.SpawnTemplatePrefix } )
   		if EventPrefix == self.SpawnTemplatePrefix or ( self.SpawnAliasPrefix and EventPrefix == self.SpawnAliasPrefix ) then
   			self.AliveUnits = self.AliveUnits + 1
   			self:T( "Alive Units: " .. self.AliveUnits )
   		end
     end
+	end
 
 end
 
@@ -1616,6 +1618,7 @@ function SPAWN:_OnDeadOrCrash( EventData )
   
 	if SpawnGroup then
 		local EventPrefix = self:_GetPrefixFromGroup( SpawnGroup )
+		if EventPrefix then -- EventPrefix can be nil if no # is found, which means, no spawnable group!
       self:T( { "Dead event: " .. EventPrefix } )
   		if EventPrefix == self.SpawnTemplatePrefix or ( self.SpawnAliasPrefix and EventPrefix == self.SpawnAliasPrefix ) then
   			self.AliveUnits = self.AliveUnits - 1
@@ -1623,6 +1626,7 @@ function SPAWN:_OnDeadOrCrash( EventData )
   		end
     end
 	end
+end
 
 --- Will detect AIR Units taking off... When the event takes place, the spawned Group is registered as airborne...
 -- This is needed to ensure that Re-SPAWNing only is done for landed AIR Groups.
@@ -1634,6 +1638,7 @@ function SPAWN:_OnTakeOff( EventData )
   local SpawnGroup = EventData.IniGroup
   if SpawnGroup then
     local EventPrefix = self:_GetPrefixFromGroup( SpawnGroup )
+    if EventPrefix then -- EventPrefix can be nil if no # is found, which means, no spawnable group!
       self:T( { "TakeOff event: " .. EventPrefix } )
       if EventPrefix == self.SpawnTemplatePrefix or ( self.SpawnAliasPrefix and EventPrefix == self.SpawnAliasPrefix ) then
     		self:T( "self.Landed = false" )
@@ -1641,6 +1646,7 @@ function SPAWN:_OnTakeOff( EventData )
       end
     end
 	end
+end
 
 --- Will detect AIR Units landing... When the event takes place, the spawned Group is registered as landed.
 -- This is needed to ensure that Re-SPAWNing is only done for landed AIR Groups.
@@ -1652,6 +1658,7 @@ function SPAWN:_OnLand( EventData )
   local SpawnGroup = EventData.IniGroup
   if SpawnGroup then
     local EventPrefix = self:_GetPrefixFromGroup( SpawnGroup )
+    if EventPrefix then -- EventPrefix can be nil if no # is found, which means, no spawnable group!
       self:T( { "Land event: " .. EventPrefix } )
       if EventPrefix == self.SpawnTemplatePrefix or ( self.SpawnAliasPrefix and EventPrefix == self.SpawnAliasPrefix ) then
   	    -- TODO: Check if this is the last unit of the group that lands.
@@ -1664,6 +1671,7 @@ function SPAWN:_OnLand( EventData )
   		end
     end
 	end
+end
 
 --- Will detect AIR Units shutting down their engines ...
 -- When the event takes place, and the method @{RepeatOnEngineShutDown} was called, the spawned Group will Re-SPAWN.
@@ -1676,6 +1684,7 @@ function SPAWN:_OnEngineShutDown( EventData )
   local SpawnGroup = EventData.IniGroup
   if SpawnGroup then
     local EventPrefix = self:_GetPrefixFromGroup( SpawnGroup )
+    if EventPrefix then -- EventPrefix can be nil if no # is found, which means, no spawnable group!
       self:T( { "EngineShutdown event: " .. EventPrefix } )
       if EventPrefix == self.SpawnTemplatePrefix or ( self.SpawnAliasPrefix and EventPrefix == self.SpawnAliasPrefix ) then
   			-- todo: test if on the runway
@@ -1688,6 +1697,7 @@ function SPAWN:_OnEngineShutDown( EventData )
   		end
     end
 	end
+end
 
 --- This function is called automatically by the Spawning scheduler.
 -- It is the internal worker method SPAWNing new Groups on the defined time intervals.