Added some ModuleService null checks

src/Discord.Net.Modules/ModuleService.cs

@@ -24,6 +24,8 @@ namespace Discord.Modules
 
 		public void Install(IModule module, string name, FilterType type)
 		{
+			if (module == null) throw new ArgumentNullException(nameof(module));
+			if (name == null) throw new ArgumentNullException(nameof(name));
 			if (_client == null) throw new InvalidOperationException("Service needs to be added to a DiscordClient before modules can be installed.");
             if (_modules.ContainsKey(module)) throw new InvalidOperationException("This module has already been added.");
 
@@ -35,6 +37,7 @@ namespace Discord.Modules
 		public ModuleManager GetManager(IModule module)
 		{
 			if (module == null) throw new ArgumentNullException(nameof(module));
+
 			ModuleManager result = null;
 			_modules.TryGetValue(module, out result);
 			return result;