config manager: overwrite defaults when unable to unmarshall values

This allows config key types to change without errors by resetting the
config with new default value

runelite-client/src/main/java/net/runelite/client/config/ConfigManager.java

@@ -507,7 +507,9 @@ public class ConfigManager
 
 			if (!override)
 			{
-				String current = getConfiguration(group.value(), item.keyName());
+				// This checks if it is set and is also unmarshallable to the correct type; so
+				// we will overwrite invalid config values with the default
+				Object current = getConfiguration(group.value(), item.keyName(), method.getReturnType());
 				if (current != null)
 				{
 					continue; // something else is already set