Fix cross thread operation when removing a reference from a project.

src/AddIns/Misc/PackageManagement/Project/Src/Design/FakePackageManagementProjectService.cs

@@ -70,6 +70,11 @@ namespace ICSharpCode.PackageManagement.Design
 			ProjectService.AddProjectItem(project, item);
 		}
 		
+		public void RemoveProjectItem(IProject project, ProjectItem item)
+		{
+			ProjectService.RemoveProjectItem(project, item);
+		}
+		
 		public void Save(IProject project)
 		{
 			project.Save();

src/AddIns/Misc/PackageManagement/Project/Src/IPackageManagementProjectService.cs

@@ -19,6 +19,7 @@ namespace ICSharpCode.PackageManagement
 		
 		void RefreshProjectBrowser();
 		void AddProjectItem(IProject project, ProjectItem item);
+		void RemoveProjectItem(IProject project, ProjectItem item);
 		void Save(IProject project);
 		
 		IEnumerable<IProject> GetOpenProjects();		

src/AddIns/Misc/PackageManagement/Project/Src/PackageManagementProjectService.cs

@@ -48,6 +48,16 @@ namespace ICSharpCode.PackageManagement
 			}
 		}
 		
+		public void RemoveProjectItem(IProject project, ProjectItem item)
+		{
+			if (WorkbenchSingleton.InvokeRequired) {
+				Action<IProject, ProjectItem> action = RemoveProjectItem;
+				WorkbenchSingleton.SafeThreadCall<IProject, ProjectItem>(action, project, item);
+			} else {
+				ProjectService.RemoveProjectItem(project, item);
+			}
+		}
+		
 		public void Save(IProject project)
 		{
 			if (WorkbenchSingleton.InvokeRequired) {

src/AddIns/Misc/PackageManagement/Project/Src/SharpDevelopProjectSystem.cs

@@ -121,8 +121,8 @@ namespace ICSharpCode.PackageManagement
 		{
 			ReferenceProjectItem referenceProjectItem = FindReference(name);
 			if (referenceProjectItem != null) {
-				ProjectService.RemoveProjectItem(project, referenceProjectItem);
-				project.Save();
+				projectService.RemoveProjectItem(project, referenceProjectItem);
+				projectService.Save(project);
 				LogRemovedReferenceFromProject(referenceProjectItem);
 			}
 		}