[fixed] delete material

[Hank]

hi there,

I delete one by one materials assigned to my object and for some step I get:

Dump written 2019-12-26_10-0
Version: 2.2.5
OS: Linux 4.15.0-54-generic x86_64
GPU: NVIDIA Corporation | GeForce GTX 650 Ti/PCIe/SSE2
Window: geom
Reason: function_clause

Short stack trace:
[{gb_trees,delete_1,2,[{file,"gb_trees.erl"},{line,408}]},
{gb_trees,delete_1,2,[{file,"gb_trees.erl"},{line,409}]},
{gb_trees,delete_1,2,[{file,"gb_trees.erl"},{line,409}]},
{gb_trees,delete,2,[{file,"gb_trees.erl"},{line,404}]},
{wings_material,delete_material,2,[{file,"wings_material.erl"},{line,131}]},
{wings_develop,time_command,2,[{file,"wings_develop.erl"},{line,87}]},
{wings,raw_command,4,[{file,"wings.erl"},{line,636}]},
{wings_wm,handle_event,3,[{file,"wings_wm.erl"},{line,1016}]},
{wings_wm,send_event,2,[{file,"wings_wm.erl"},{line,982}]},
{wings_wm,do_dispatch,2,[{file,"wings_wm.erl"},{line,883}]},
{wings_wm,dispatch_event,1,[{file,"wings_wm.erl"},{line,792}]},
{wings_wm,get_and_dispatch,0,[{file,"wings_wm.erl"},{line,681}]},
{wings,init_part2,3,[{file,"wings.erl"},{line,108}]},
{proc_lib,init_p_do_apply,3,[{file,"proc_lib.erl"},{line,249}]}]

Long stack trace:
[{gb_trees,delete_1,[chrome,nil],[{file,"gb_trees.erl"},{line,408}]},
{gb_trees,delete_1,2,[{file,"gb_trees.erl"},{line,409}]},
{gb_trees,delete_1,2,[{file,"gb_trees.erl"},{line,409}]},
{gb_trees,delete,2,[{file,"gb_trees.erl"},{line,404}]},
{wings_material,delete_material,2,[{file,"wings_material.erl"},{line,131}]},
{wings_develop,time_command,2,[{file,"wings_develop.erl"},{line,87}]},
{wings,raw_command,4,[{file,"wings.erl"},{line,636}]},
{wings_wm,handle_event,3,[{file,"wings_wm.erl"},{line,1016}]},
{wings_wm,send_event,2,[{file,"wings_wm.erl"},{line,982}]},
{wings_wm,do_dispatch,2,[{file,"wings_wm.erl"},{line,883}]},
{wings_wm,dispatch_event,1,[{file,"wings_wm.erl"},{line,792}]},
{wings_wm,get_and_dispatch,0,[{file,"wings_wm.erl"},{line,681}]},
{wings,init_part2,3,[{file,"wings.erl"},{line,108}]},
{proc_lib,init_p_do_apply,3,[{file,"proc_lib.erl"},{line,249}]}]

No particular step is followed for this operation. Just LMB on the material and delete key.

[update]
I've just find out it's related with quick delete key press step. Thus, any material which is removed with 2xdelete, cause the issue.
Tried with new scene and it doesn't work like this

BR, Hank