Prevent duplicate monolith generation in multifaction (#563)

Due to changes in #508, an Exorider is now spawned on every newly generated multifaction map. However, this also caused a Monolith to be generated each time, resulting in multiple Monoliths appearing and causing issues.

This update adds a Harmony patch to GenStep_Monolith.GenerateMonolith to skip Monolith generation if one already exists.

Author: Tick-git

Source/Client/Factions/MultifactionPatches.cs

@@ -408,6 +408,22 @@ private static int MakeIdPositive(int id)
     }
 }
 
+#region Map generation
+
+[HarmonyPatch(typeof(GenStep_Monolith), nameof(GenStep_Monolith.GenerateMonolith))]
+public static class GenStepMonolithPatch
+{
+    static bool Prefix()
+    {
+        if (Multiplayer.Client == null)
+            return true;
+
+        var anomalyComp = Current.Game.components.OfType<GameComponent_Anomaly>().FirstOrDefault();
+
+        return anomalyComp?.monolith == null;
+    }
+}
+
 [HarmonyPatch(typeof(ScenPart_ScatterThings), nameof(ScenPart_ScatterThings.GenerateIntoMap))]
 static class ScenPartScatterThingsPatch
 {
@@ -426,6 +442,8 @@ static bool Prefix()
     }
 }
 
+#endregion
+
 [HarmonyPatch(typeof(CharacterCardUtility), nameof(CharacterCardUtility.DoTopStack))]
 static class CharacterCardUtilityDontDrawIdeoPlate
 {