Fix "Unhandled exception when installing packed addin with incorrect .addin file" (http://community.sharpdevelop.net/forums/t/11807.aspx)

src/Main/Core/Project/Src/AddInTree/AddIn/AddIn.cs

@@ -267,6 +267,7 @@ namespace ICSharpCode.Core
 		
 		public static AddIn Load(TextReader textReader, string hintPath)
 		{
+			try {
 				AddIn addIn = new AddIn();
 				using (XmlTextReader reader = new XmlTextReader(textReader)) {
 					while (reader.Read()){
@@ -283,6 +284,9 @@ namespace ICSharpCode.Core
 					}
 				}
 				return addIn;
+			} catch (XmlException ex) {
+				throw new AddInLoadException(ex.Message, ex);
+			}
 		}
 		
 		public static AddIn Load(string fileName)