Remove HashMap from Config and add runtime Config type checking

HashMap isn't supported by NightConfig and can cause the game to crash in some situations

core/src/main/java/com/seibel/distanthorizons/core/config/Config.java

@@ -1125,10 +1125,6 @@ public class Config
 							.set(new ArrayList<String>(Arrays.asList("option 1", "option 2", "option 3")))
 							.build();
 					
-					public static ConfigEntry<Map<String, String>> mapTest = new ConfigEntry.Builder<Map<String, String>>()
-							.set(new HashMap<String, String>())
-							.build();
-					
 					public static ConfigCategory categoryTest = new ConfigCategory.Builder().set(CategoryTest.class).build();
 					
 					public static ConfigEntry<Integer> linkableTest = new ConfigEntry.Builder<Integer>()

core/src/main/java/com/seibel/distanthorizons/core/config/types/ConfigEntry.java

@@ -7,8 +7,12 @@ import com.seibel.distanthorizons.core.config.types.enums.EConfigEntryAppearance
 import com.seibel.distanthorizons.core.config.types.enums.EConfigEntryPerformance;
 import com.seibel.distanthorizons.coreapi.interfaces.config.IConfigEntry;
 
+import java.time.temporal.Temporal;
 import java.util.ArrayList;
 import java.util.Arrays;
+import java.util.List;
+
+import static com.electronwill.nightconfig.core.NullObject.NULL_OBJECT;
 
 /**
  * Use for making the config variables
@@ -40,6 +44,29 @@ public class ConfigEntry<T> extends AbstractConfigType<T, ConfigEntry<T>> implem
     private ConfigEntry(EConfigEntryAppearance appearance, T value, String comment, T min, T max, boolean allowApiOverride, EConfigEntryPerformance performance, ArrayList<IConfigListener> listenerList)
 	{
         super(appearance, value);
+		
+		// runtime check to make sure the config value is supported by NightConfig,
+		// unfortunately we can't do this type of check statically without Java 16
+		if (value == null)
+		{
+			throw new IllegalArgumentException("ConfigEntry setup failure. TOML doesn't support saving null values.");
+		}
+		// all of these types were taken from NightConfig's writing code
+		else if (!(value instanceof List)
+				&& !(value instanceof CharSequence) // String
+				&& !(value instanceof Enum)
+				&& !(value instanceof Temporal) // Date or DateTime
+				&& !(value instanceof Float || value instanceof Double)
+				&& !(value instanceof Number)
+				&& !(value instanceof Boolean)
+				// optional type that is specific to NightConfig, currently commented out so we aren't tied quite so tightly to NightConfig
+				//&& !(value instanceof Config) // NightConfig interface
+				)
+		{
+			throw new IllegalArgumentException("ConfigEntry setup failure. Value type ["+value.getClass()+"] is not supported by NightConfig.");
+		}
+		
+		
         this.defaultValue = value;
         this.comment = comment;
         this.min = min;