Weird error upon importing an .smd file in Blender

[DenDro]

Alright so I'm trying to make a custom model for tf2 which is almost identical to the stock. After exporting one smd file, I realised that I haven't added the other LOD models yet and so I tried importing them and it showed this error report:

bpy.context.scene.layers[1] = True
bpy.ops.object.editmode_toggle()
bpy.ops.object.posemode_toggle()
bpy.ops.pose.armature_apply()
bpy.ops.object.posemode_toggle()
bpy.ops.object.editmode_toggle()
Traceback (most recent call last):
File "C:\Users\Wolly\AppData\Roaming\Blender Foundation\Blender\2.79\scripts\addons\io_scene_valvesource\import_smd.py", line 72, in execute
self.num_files_imported = self.readSMD(filepath, self.properties.upAxis, self.properties.rotMode)
File "C:\Users\Wolly\AppData\Roaming\Blender Foundation\Blender\2.79\scripts\addons\io_scene_valvesource\import_smd.py", line 1247, in readSMD
if line == "skeleton\n": self.readFrames()
File "C:\Users\Wolly\AppData\Roaming\Blender Foundation\Blender\2.79\scripts\addons\io_scene_valvesource\import_smd.py", line 424, in readFrames
self.applyFrames(keyframes,num_frames)
File "C:\Users\Wolly\AppData\Roaming\Blender Foundation\Blender\2.79\scripts\addons\io_scene_valvesource\import_smd.py", line 476, in applyFrames
for bone in [smd.a.data.edit_bones[b.name] for b in keyframes.keys()]:
File "C:\Users\Wolly\AppData\Roaming\Blender Foundation\Blender\2.79\scripts\addons\io_scene_valvesource\import_smd.py", line 476, in <listcomp>
for bone in [smd.a.data.edit_bones[b.name] for b in keyframes.keys()]:
KeyError: 'bpy_prop_collection[key]: key "c_weapon_stattrack" not found'

location: <unknown location>:-1

bpy.ops.object.editmode_toggle()
bpy.ops.object.posemode_toggle()
bpy.ops.pose.armature_apply()
bpy.ops.object.posemode_toggle()
bpy.ops.object.editmode_toggle()
Traceback (most recent call last):
File "C:\Users\Wolly\AppData\Roaming\Blender Foundation\Blender\2.79\scripts\addons\io_scene_valvesource\import_smd.py", line 72, in execute
self.num_files_imported = self.readSMD(filepath, self.properties.upAxis, self.properties.rotMode)
File "C:\Users\Wolly\AppData\Roaming\Blender Foundation\Blender\2.79\scripts\addons\io_scene_valvesource\import_smd.py", line 1247, in readSMD
if line == "skeleton\n": self.readFrames()
File "C:\Users\Wolly\AppData\Roaming\Blender Foundation\Blender\2.79\scripts\addons\io_scene_valvesource\import_smd.py", line 424, in readFrames
self.applyFrames(keyframes,num_frames)
File "C:\Users\Wolly\AppData\Roaming\Blender Foundation\Blender\2.79\scripts\addons\io_scene_valvesource\import_smd.py", line 476, in applyFrames
for bone in [smd.a.data.edit_bones[b.name] for b in keyframes.keys()]:
File "C:\Users\Wolly\AppData\Roaming\Blender Foundation\Blender\2.79\scripts\addons\io_scene_valvesource\import_smd.py", line 476, in <listcomp>
for bone in [smd.a.data.edit_bones[b.name] for b in keyframes.keys()]:
KeyError: 'bpy_prop_collection[key]: key "c_weapon_stattrack" not found'

location: <unknown location>:-1

I tried to find solutions but I can't find anyone who has a similar problem to me.

Some info:

I'm using Blender 2.79 (From steam and probably not the latest one)
Blender Source Tools 2.10.2 (Installed the thing correctly usable at first but not now as I'm writing this post)
Windows 10, 64 bit

Thanks in advance!

[Artfunkel]

Looks like the LOD you're trying to import references a non-existent bone. Try changing the Bone Append Mode when you import to Validate Against Target.

[DenDro]

Originally posted by Artfunkel:

Looks like the LOD you're trying to import references a non-existent bone. Try changing the Bone Append Mode when you import to Validate Against Target.

I'm sorry but how do I do that? Is "Validate Against Target" some function that I can access from the screen or do I have to execute some buttons/do something else? Whereas for Bone Append Mode, googling it doesn't really tell me any thing and instead proceeds to talk all about bones.

So in all, step by step, what do I have to do to be able to import the "LOD that references a non-existent bone."

Side note:
Even when I tried importing the SAME smd I used earlier to make my model, it gives me the same error. (the smd that i used to make my model have a skeleton. not sure whether the skeleton is related to the bone append part but yeah.)

[Artfunkel]

It's one of the options in the bottom left of the import window.