Fix SD-1886 - Renaming multiple controls in forms designer causes crash with data loss

Fixed ParseableFileContentFinder to use the latest version of files opened in secondary view contents.
We were only looking at primary view contents and ignoring secondary view contents, so the rename operation was looking at the old version of the Designer.cs file.

src/Main/Base/Project/Src/Services/ProjectService/ParseableFileContentFinder.cs

@@ -16,7 +16,7 @@ namespace ICSharpCode.SharpDevelop.Project
 	/// </summary>
 	public class ParseableFileContentFinder
 	{
-		FileName[] viewContentFileNamesCollection = WorkbenchSingleton.SafeThreadFunction(FileService.GetOpenFiles).ToArray();
+		FileName[] viewContentFileNamesCollection = WorkbenchSingleton.SafeThreadFunction(() => FileService.OpenedFiles.Select(f => f.FileName).ToArray());
 		
 		/// <summary>
 		/// Retrieves the file contents for the specified project items.