heres the error message
The mod Cerys (2.1.7) caused a non-recoverable error.
Please report this error to the mod author.

Error while running event Cerys-Moon-of-Fulgora::on_tick (ID 0)
Cerys-Moon-of-Fulgora/scripts/lighting.lua:132: attempt to index field 'flag_rendering_1' (a nil value)
stack traceback:
Cerys-Moon-of-Fulgora/scripts/lighting.lua:132: in function 'tick_3_update_lights'
Cerys-Moon-of-Fulgora/scripts/events.lua:172: in function 'cerys_tick'
Cerys-Moon-of-Fulgora/scripts/events.lua:147: in function <Cerys-Moon-of-Fulgora/scripts/events.lua:123>

here are my mods enabled
base
elevated-rails
quality
space-age
aai-containers
aai-loaders
aai-programmable-vehicles
aai-signal-transmission
aai-signals
aai-vehicles-chaingunner
aai-vehicles-flame-tank
aai-vehicles-flame-tumbler
aai-vehicles-hauler
aai-vehicles-ironclad
aai-vehicles-laser-tank
aai-vehicles-miner
aai-vehicles-warden
AfraidOfTheDark
Age-of-Production
alien-biomes
alien-biomes-graphics
AncientDrill
any-planet-start
AoP-extended-planets
ArmouredBiters
AutoDeconstruct
automatic-logistic-chests
Better_Starmap_Background
bobinserters
Bottleneck
bullet-trails
cargo-ships
cargo-ships-graphics
castra
Cerys-Moon-of-Fulgora
Cerys-Re-enable-Productivity
combat-mechanics-overhaul
common-prototypes
common-prototypes-graphics
Constructron-Continued
corrundum
Cosmic-Social-Distancing
DiscoScience
dredgeworks
dredgeworks-graphics
dw-frozen-reaches
equipment-gantry
factorissimo-2-notnotmelon
far-reach
Flare Stack
flib
Flow Control
FluidMustFlow
foundry-restructuring
fulgora-extended
grappling-gun
hd_planets
how-it-should-have-started
hurricane-graphics
informatron
jetpack
Kux-CoreLib
Kux-OrbitalIonCannon
large-storage-tank
maraxsis
metal-and-stars
metal-and-stars-graphics
metal-and-stars-graphics-2
Milestones
modules-t4
Moshine
Moshine-assets
MyQuickStart
orbital-transfer
Pi-C_lib
Planet-Hopper
planet-muluna
PlanetsLib
Redrawn-Space-Connections
RenaiTransportation
Repair_Turret
RoboticsFacility
RPGsystem
se-space-trains
secretas
shield-projector
snouz-big-accumulator
snouz-big-solar-panel
SpidertronEnhancements
SpidertronPatrols
squeak-through-2
stirling-generator
Subsurface
tenebris-prime
tree_collision
valves
visible-planets
Wood_Gasification_updated

This is fixed.

"Hi, I’m a bit of a noob when it comes to programming and anything code-related. I also wanted to add Cerys to my current save file—standard SA, no QAL. It’s giving me the following error (error below). Additionally, I ran the current build in the ‘Start Game with Cerys’ mode, and everything works. My question is: can this be fixed in the future, or should I start the map from the beginning?"

Error while running event Cerys-Moon-of-Fulgora::on_tick (ID 0)
Cerys-Moon-of-Fulgora/scripts/lighting.lua:42: attempt to index field 'light' (a nil value)
stack traceback:
Cerys-Moon-of-Fulgora/scripts/lighting.lua:42: in function 'tick_3_update_lights'
Cerys-Moon-of-Fulgora/scripts/events.lua:172: in function 'cerys_tick'
Cerys-Moon-of-Fulgora/scripts/events.lua:147: in function <Cerys-Moon-of-Fulgora/scripts/events.lua:123>

Hi Oleg, this issue should be fixed in Cerys 2.1.9.