I get this message when trying to launch with it enabled (mod version 3.0.2)

Failed to load mods: bobwarfare/data-final-fixes.lua:120: attempt to index field 'action' (a nil value)
stack traceback:
bobwarfare/data-final-fixes.lua:120: in main chunk

I'm getting the same error. Looking at the source it is inside a compatibility check for Earendal's Combat Mechanics Overhaul. You have that installed and enabled by any chance? I know I do.

[edit]
Oops. hit submit too soon. Forgot to say if I disable that mod it loads fine.

Yeah you're spot on, had it installed and if I disable it Bob's Warfare loads just fine

That's certainly a preferable exchange of mods if I can only have one right now

based on what I can tell from the surrounding lines for similar shotgun projectile types, the target_effects[2] on that line (in data-final-fixes.lua) should be a 1, fixed it for me

However fixing that gave another error in data-final-fixes, which originated in prototypes/entity/projectiles.lua.
Looks like the second "action" table has an extra bracket on line 1715 (and 1730), commenting those out fixed it.
the error for it said line 1866, but that seems to be the first call to the function and not the cause.

I get the following today. This is the only mod that has an issue.

Failed to load mods: bobwarfare/data-final-fixes.lua:120: attempt to index field 'action' (a nil value)
stack traceback:
bobwarfare/data-final-fixes.lua:120: in main chunk

There is a PullRequest on the GitHub with a fix for this
https://github.com/modded-factorio/bobsmods/pull/638/files

If you have something like NotePad++ or VisuaStudio, you can update the .LUA file with the following changes

Line 119
"data.raw.projectile["bob-shotgun-explosive-projectile"].action.action_delivery.target_effects[2].action.force ="
Change it to
"data.raw.projectile["bob-shotgun-explosive-projectile"].action.action_delivery.target_effects[1].action.force ="

Line 125
"data.raw.projectile["bob-shotgun-plasma-projectile"].action.action_delivery.target_effects[1].action.force ="
Change it to
"data.raw.projectile["bob-shotgun-plasma-projectile"].action.action_delivery.target_effects[1].action[1].force ="

I was able to get to main menu and didn't have the warning popup after implementing the fix outlined in the GitHub PullRequest above

Cheers! Changing those two lines does indeed make both mods launch without issues, and seems to work fine with my old save as well so far

If anyone isn't comfortable with making those edits, you can also temporarily solve the issue by turning the CMO setting "Shotguns Hit Friendly" on.