Add back fall damage block for local explosion cheats

Vanilla commit:

a02294421c

SQF/dayz_code/init/variables.sqf

@@ -592,6 +592,7 @@ if (!isDedicated) then {
 	dayz_temperaturmin = 27; //TeeChange
 
 	//player special variables
+	dayz_lastDamageSourceNull = false;
 	dayz_lastDamageSource = "none";
 	dayz_lastDamageTime = 0;
 	dayz_lastMedicalSource = "none";