Error getting GM:S to find variable.

In my game I have set a global variable (global.weapon 0;) under the my main control object.

Then when I have set this bit of code for my weapon:

x_offset = global.weaponArray[global.weapon,5];
y_offset = global.weaponArray[global.weapon,6];
my_gun = instance_create(x + x_offset, y + y_offset, obj_gun);



However I receive the following error:

___________________________________________
################################################## ##########################################
FATAL ERROR in
action number 1
of Create Event
for object obj_player:
Push :: Execution Error - Variable Get -5.weapon(100015, -2147483648)
at gml_Object_obj_player_CreateEvent_1 (line 8) - x_offset = global.weaponArray[global.weapon,5];
################################################## ##########################################


How would I be able to fix this?