[Completion] Fixed little completion issue.

ICSharpCode.NRefactory.CSharp/Completion/CSharpCompletionEngine.cs

@@ -1787,9 +1787,11 @@ namespace ICSharpCode.NRefactory.CSharp.Completion
 					}
 					if (hintType is ParameterizedType && hintType.TypeParameterCount == 1 && hintType.FullName == "System.Collections.Generic.IEnumerable") {
 						var arg = ((ParameterizedType)hintType).TypeArguments.FirstOrDefault();
+						if (arg.Kind != TypeKind.TypeParameter) {
 							var array = new ArrayTypeReference(arg.ToTypeReference(), 1).Resolve(ctx);
 							wrapper.AddType(array, amb.ConvertType(array));
 						}
+					}
 				} else {
 					var hint = wrapper.AddType(hintType, DefaultCompletionString);
 					if (hint != null) {