Change classes that use FieldLoader to use read-only collections.

OpenRA.Mods.Common/Projectiles/GravityBomb.cs

@@ -10,6 +10,7 @@
 #endregion
 
 using System.Collections.Generic;
+using System.Collections.Immutable;
 using OpenRA.GameRules;
 using OpenRA.Graphics;
 using OpenRA.Primitives;
@@ -24,7 +25,7 @@ namespace OpenRA.Mods.Common.Projectiles
 
 		[SequenceReference(nameof(Image), allowNullImage: true)]
 		[Desc("Loop a randomly chosen sequence of Image from this list while falling.")]
-		public readonly string[] Sequences = ["idle"];
+		public readonly ImmutableArray<string> Sequences = ["idle"];
 
 		[SequenceReference(nameof(Image), allowNullImage: true)]
 		[Desc("Sequence to play when launched. Skipped if null or empty.")]