Fix null reference exception when accessing EnvDTE.CodeType.Bases for System.Object.

src/AddIns/Misc/PackageManagement/Project/Src/EnvDTE/CodeTypeBaseTypes.cs

@@ -20,7 +20,9 @@ namespace ICSharpCode.PackageManagement.EnvDTE
 		
 		void AddBaseTypes()
 		{
-			AddCodeElement(CodeClass2.CreateFromBaseType(projectContent, c.BaseType));
+			if (c.BaseType != null) {
+				AddCodeElement(CodeClass2.CreateFromBaseType(projectContent, c.BaseType));
+			}
 		}
 	}
 }

src/AddIns/Misc/PackageManagement/Test/Src/EnvDTE/CodeClass2Tests.cs

@@ -171,6 +171,17 @@ namespace PackageManagement.Tests.EnvDTE
 			Assert.AreEqual("Object", baseClass.Name);
 		}
 		
+		[Test]
+		public void BaseTypes_ClassBaseTypeIsNull_ReturnsNoCodeElements()
+		{
+			CreateProjectContent();
+			CreatePublicClass("System.Object");
+			
+			CodeElements codeElements = codeClass.Bases;
+			
+			Assert.AreEqual(0, codeElements.Count);
+		}
+		
 		[Test]
 		public void Members_ClassHasOneMethod_ReturnsOneMethod()
 		{