App crash with bug type 120.

I had an app running on the foreground when it suddenly crashed. I got no crash report from the app. Can someone help me understand what this log says? Did this OS crash the app intentionally to protect the battery ?

{"bug_type":"120","os_version":"iPhone OS 12.3.1 (16F203)"}

Incident Identifier: A36994B2-4EF8-465E-AB2D-5358BBDE8DF0

CrashReporter Key: (null)

Date: 2020-02-11 19:02:13 +0000

OS Version: iPhone OS 12.3.1 (16F203)

mediaserverd: com.apple.audio.VAD [vdef] AggDev 15.context.preventuseridlesleep PreventUserIdleSystemSleep == 255, held for 00:20:08

mediaserverd: MediaExperience.sid:0x1a3f6, DartsOfFury(1104), 'prim'(uk.co.yakuto.DartsOfFury).isplaying NoIdleSleepAssertion == 255, held for 00:35:20

assertiond: DartsOfFury:1104:1104-EBEA7451-6D95-4514-AE45-191CABB72933 [Shared Background Assertion 0 for uk.co.yakuto.DartsOfFury] [0x100f41bd0]/26-CEAD1CEA-6016-43FA-9826-C3AC551297A2 [MediaExperience.1104."uk.co.yakuto.DartsOfFury"."AmbientSound".isPlayingProcessAssertion] [0x100e1d260] SystemIsActive == 255, held for 00:35:30

assertiond: SpringBoard:52:52-9C87D145-62B7-41D1-AA45-53410B859B18 [FBSystemApp] [0x100e1cb50] SystemIsActive == 255, held for 03:14:04

Foreground Applications: uk.co.yakuto.DartsOfFury

Screen Brightness: 0.760000

Hardware Model: N56AP

Awake Time: 03:14:04 (11643)

Standby Time: 03:14:04 (11643)

Partial Charge: 1

Capacity: 1

Voltage: 3416 mV

Voltage Droop Time: 312121

Voltage Droop Transitions: 148