Fix warning

Author: ufechner7

test/plotting/test_plotting.jl

@@ -30,16 +30,16 @@ safe_rm(path) = begin
     nothing
 end
 
-if !@isdefined ram_wing
+let
     body_path = joinpath(tempdir(), "ram_air_kite_body.obj")
     foil_path = joinpath(tempdir(), "ram_air_kite_foil.dat")
     body_src = joinpath(_ram_data_dir, "ram_air_kite_body.obj")
     foil_src = joinpath(_ram_data_dir, "ram_air_kite_foil.dat")
     cp(body_src, body_path; force=true)
     cp(foil_src, foil_path; force=true)
-    ram_wing = ObjWing(body_path, foil_path;
-                       alpha_range=deg2rad.(-1:1),
-                       delta_range=deg2rad.(-1:1))
+    global ram_wing = ObjWing(body_path, foil_path;
+                              alpha_range=deg2rad.(-1:1),
+                              delta_range=deg2rad.(-1:1))
 end
 
 function create_body_aero()