I got the same error as a few other people on here I think. However, updating to the latest version did nothing for me.
It's on a multiplayer server and the only other person playing can enter and exit just fine.

Here's the error message:

145.432 Error MainLoop.cpp:1173: Exception at tick 73600811: The mod The Blueprint Lab - Bud caused a non-recoverable error.
Please report this error to the mod author.

Error while running event BlueprintLab_Bud17::on_gui_click (ID 1)
LuaEntity API call when LuaEntity was invalid.
stack traceback:
BlueprintLab_Bud17/scripts/logic.lua:64: in function 'ToTheWorld'
BlueprintLab_Bud17/scripts/logic.lua:9: in function 'OnLabButton'
BlueprintLab_Bud17/scripts/gui.lua:30: in function <BlueprintLab_Bud17/scripts/gui.lua:28>
stack traceback:
[C]: in function 'index'
__BlueprintLab_Bud17/scripts/logic.lua:64: in function 'ToTheWorld'
BlueprintLab_Bud17/scripts/logic.lua:9: in function 'OnLabButton'
BlueprintLab_Bud17/scripts/gui.lua:30: in function <BlueprintLab_Bud17/scripts/gui.lua:28
145.432 Error ServerMultiplayerManager.cpp:92: MultiplayerManager failed: "The mod The Blueprint Lab - Bud caused a non-recoverable error.
Please report this error to the mod author.

Error while running event BlueprintLab_Bud17::on_gui_click (ID 1)
LuaEntity API call when LuaEntity was invalid.
stack traceback:
BlueprintLab_Bud17/scripts/logic.lua:64: in function 'ToTheWorld'
BlueprintLab_Bud17/scripts/logic.lua:9: in function 'OnLabButton'
BlueprintLab_Bud17/scripts/gui.lua:30: in function <BlueprintLab_Bud17/scripts/gui.lua:28>
stack traceback:
[C]: in function 'index'
__BlueprintLab_Bud17/scripts/logic.lua:64: in function 'ToTheWorld'
BlueprintLab_Bud17/scripts/logic.lua:9: in function 'OnLabButton'
BlueprintLab_Bud17/scripts/gui.lua:30: in function <BlueprintLab_Bud17/scripts/gui.lua:28>
145.432 Info ServerMultiplayerManager.cpp:769: updateTick(73600811) changing state from(InGame) to(Failed)
145.433 Quitting: multiplayer error.

These are all the mods I'm running:
{
"mods":
[

{
  "name": "base",
  "enabled": true
},

{
  "name": "A Sea Block Config",
  "enabled": true
},

{
  "name": "advanced-combinator",
  "enabled": true
},

{
  "name": "angelsaddons-warehouses",
  "enabled": true
},

{
  "name": "angelsbioprocessing",
  "enabled": true
},

{
  "name": "angelspetrochem",
  "enabled": true
},

{
  "name": "angelsrefining",
  "enabled": true
},

{
  "name": "angelssmelting",
  "enabled": true
},

{
  "name": "BlueprintLab_Bud17",
  "enabled": true
},

{
  "name": "bobassembly",
  "enabled": true
},

{
  "name": "bobelectronics",
  "enabled": true
},

{
  "name": "bobenemies",
  "enabled": true
},

{
  "name": "bobinserters",
  "enabled": true
},

{
  "name": "boblibrary",
  "enabled": true
},

{
  "name": "boblogistics",
  "enabled": true
},

{
  "name": "bobmining",
  "enabled": true
},

{
  "name": "bobmodules",
  "enabled": true
},

{
  "name": "bobplates",
  "enabled": true
},

{
  "name": "bobpower",
  "enabled": true
},

{
  "name": "bobrevamp",
  "enabled": true
},

{
  "name": "bobtech",
  "enabled": true
},

{
  "name": "bobvehicleequipment",
  "enabled": true
},

{
  "name": "bobwarfare",
  "enabled": true
},

{
  "name": "Bottleneck",
  "enabled": true
},

{
  "name": "CircuitProcessing",
  "enabled": true
},

{
  "name": "even-distribution",
  "enabled": true
},

{
  "name": "Explosive Excavation",
  "enabled": true
},

{
  "name": "FNEI",
  "enabled": true
},

{
  "name": "helmod-optimized",
  "enabled": true
},

{
  "name": "KS_Power",
  "enabled": true
},

{
  "name": "LandfillPainting",
  "enabled": true
},

{
  "name": "LoaderRedux",
  "enabled": true
},

{
  "name": "LogisticTrainNetwork",
  "enabled": true
},

{
  "name": "LTN_Tracker",
  "enabled": true
},

{
  "name": "MaxRateCalculator",
  "enabled": true
},

{
  "name": "Nanobots",
  "enabled": true
},

{
  "name": "Nuclear Fuel",
  "enabled": true
},

{
  "name": "omnilib",
  "enabled": true
},

{
  "name": "omnimatter_permutation",
  "enabled": true
},

{
  "name": "OpteraLib",
  "enabled": true
},

{
  "name": "PickerAtheneum",
  "enabled": true
},

{
  "name": "PickerBlueprinter",
  "enabled": true
},

{
  "name": "qol_research",
  "enabled": true
},

{
  "name": "ScienceCostTweakerM",
  "enabled": true
},

{
  "name": "SeaBlock",
  "enabled": true
},

{
  "name": "SeaBlockMetaPack",
  "enabled": true
},

{
  "name": "ShinyAngelGFX",
  "enabled": true
},

{
  "name": "ShinyBobGFX",
  "enabled": true
},

{
  "name": "SpaceMod",
  "enabled": true
},

{
  "name": "Squeak Through",
  "enabled": true
},

{
  "name": "stdlib",
  "enabled": true
},

{
  "name": "train-pubsub",
  "enabled": true
},

{
  "name": "underground-pipe-pack",
  "enabled": true
},

{
  "name": "visual-signals",
  "enabled": true
},

{
  "name": "Warehousing",
  "enabled": true
}

]
}