Fix null reference when building a project.

Pre-build custom tool runner was not handling that IProject.ProjectSpecificItems can be null for a project that has no preferences xml file already created (e.g. project created by Visual Studio and then opened in SharpDevelop).

src/Main/Base/Project/Src/Project/ProjectCustomToolOptions.cs

@@ -19,7 +19,11 @@ namespace ICSharpCode.SharpDevelop.Project
 		
 		void GetCustomToolProperties(IProject project)
 		{
-			properties = project.ProjectSpecificProperties.Get("customTool", new Properties());
+			if (project.ProjectSpecificProperties != null) {
+				properties = project.ProjectSpecificProperties.Get("customTool", new Properties());
+			} else {
+				properties = new Properties();
+			}
 		}
 		
 		public bool RunCustomToolOnBuild {

src/Main/Base/Test/Project/BeforeBuildCustomToolProjectItemsTests.cs

@@ -23,10 +23,16 @@ namespace ICSharpCode.SharpDevelop.Tests.Project
 		
 		IProject CreateProject(string fileName = @"d:\MyProject\MyProject.csproj")
 		{
-			projectHelper = new ProjectHelper(fileName);
+			CreateProjectWithNoProjectSpecifiedProperties(fileName);
+			projectHelper.AddProjectSpecificProperties();
 			return projectHelper.Project;
 		}
 		
+		void CreateProjectWithNoProjectSpecifiedProperties(string fileName)
+		{
+			projectHelper = new ProjectHelper(fileName);
+		}
+		
 		void CreateSolution(params IProject[] projects)
 		{
 			IProjectChangeWatcher watcher = MockRepository.GenerateStub<IProjectChangeWatcher>();
@@ -263,5 +269,16 @@ namespace ICSharpCode.SharpDevelop.Tests.Project
 			};
 			CollectionAssert.AreEqual(expectedProjectItems, projectItems);
 		}
+		
+		[Test]
+		public void GetProjectItems_ProjectSpecificPropertiesIsNull_NoProjectItemsReturnedAndNoNullReferenceExceptionThrown()
+		{
+			CreateProjectWithNoProjectSpecifiedProperties(@"d:\MyProject\FirstProject.csproj");
+			CreateBeforeBuildCustomToolProjectItems();
+			
+			List<FileProjectItem> projectItems = GetProjectItems();
+			
+			Assert.AreEqual(0, projectItems.Count);
+		}
 	}
 }

src/Main/Base/Test/Utils/ProjectHelper.cs

@@ -25,10 +25,14 @@ namespace ICSharpCode.SharpDevelop.Tests.Utils
 				.Return(null)
 				.WhenCalled(mi => mi.ReturnValue = new ReadOnlyCollection<ProjectItem>(ProjectItems));
 			
-			Project.Stub(p => p.ProjectSpecificProperties).Return(ProjectSpecificProperties);
 			Project.Stub(p => p.SyncRoot).Return(new Object());
 		}
 		
+		public void AddProjectSpecificProperties()
+		{
+			Project.Stub(p => p.ProjectSpecificProperties).Return(ProjectSpecificProperties);
+		}
+		
 		public void AddProjectItem(ProjectItem projectItem)
 		{
 			ProjectItems.Add(projectItem);