Question Mesh has vertices with no weight and bone assigned

I'm trying to figure out what is the best way to solve this issue I get when importing an animated inanimate object.
The error is

ImportFBX Warnings:

Mesh 'gate_wood' has 28 (out of 68) vertices with no weight and bone assigned (they will be assigned to bone #0 with weight 1). The list of vertices: 0, 1, 2, 3, 4, 5, 6, 7, 9, 10 and so on...

The problem is that not having a bone assigned is intended. The object is a gate, and when the animation is played, the frame should stay in the same place, and only the doors open. Unfortunately, because of the way Unity auto-assigns the vertices to a bone, the entire frame swings with the left door.

What would I need to do in Blender to fix this? I don't have a lot of Blender animation experience, so a simple explanation for a 5 year old would be great

 

For anyone else that has this same problem and finds this forum post in the future, I solved it by selecting all vertices that weren't part of a vertex group, and then splitting them into a separate submesh and removing all animation, vertex group, and armature modifiers from the submesh in Blender before exporting the FBX.

I'm not sure if this is a good or bad solution, but if anyone else has a better solution, please feel free to post it here.

 

I have a problem like this during the day and I got the solution thanks to this video

Unity Error! Mesh 4931 (out of 4931) vertices with no weight and bone assigned - YouTube