I did some digging around in the gun.lua file (as someone who has no idea how to code in lua). From what I can tell, there are 2 solutions to the issue, with the first being to delete the 18th line of the file (which is "tankAC.attack_parameters.sound[1].volume = 0.5 --1.0" without quotes) and save, which I assume would likely mean that some audio wouldn't play, but I also got it to work by changing the line to "tankAC.attack_parameters.sound.volume = 0.5 --1.0" (without quotes), however I don't know if that has any repercussions.
(Also, not saying you do or don't know code if it comes across that way, just covering everything so everyone can understand ^^ )
Lets take the following:
sound = {
filename = "FILENAME",
volume: 0.6
}
So, when you have a array like above, there's a few different ways to set or get data from the array.
You can do sound[0], or sound[1], which since numbering systems start at 0 in (all? most) languages, that would give you sound.filename, and sound.volume respectively. Alternatively, if you know the name of the variable itself, you can just do sound.filename, or sound.volume.
I don't know if it changed between mod updates, but line 18 is asking for sound[1].volume, which would look like this:
sound = {
filename = "FILENAME",
volume: {
volume: 0.6
}
}
So your fix of changing sound[1].volume to sound.volume is one of two real possible fixes (the other being sound[1]), and shouldn't actually break anything.