Fix some build warnings

Include:
Warning	CS0168	The variable 'ex' is declared but never used
Warning	CS0649	Field 'EditModel.AutoBookmarkStyle.MatchPattern' is never assigned to, and will always have its default value null
Warning	CS0649	Field 'BookmarkElement.AutoLevel' is never assigned to, and will always have its default value 0

App/Common/ValueHelper.cs

@@ -31,7 +31,7 @@ public static TDisposable TryDispose<TDisposable>(this TDisposable disposable)
 				try {
 					disposable.Dispose();
 				}
-				catch (Exception ex) {
+				catch (Exception) {
 					// ignore
 				}
 			}

App/Functions/Editor/BookmarkEditorView.cs

@@ -449,7 +449,7 @@ internal void PasteBookmarks(XmlElement target, bool asChild) {
 				}
 				CopyOrMoveElement(_copiedBookmarks, target, asChild, true, true, c || OperationAffectsDecendants);
 			}
-			catch (Exception ex) {
+			catch (Exception) {
 				// ignore
 			}
 		}

App/Functions/Editor/EditModel.cs

@@ -75,7 +75,7 @@ internal sealed class AutoBookmarkStyle
 			internal readonly string FontName;
 			internal readonly int FontSize;
 			internal readonly BookmarkSettings Style;
-			internal MatchPattern MatchPattern;
+			internal MatchPattern MatchPattern = null;
 
 			internal int Level;
 

App/MainForm.cs

@@ -230,7 +230,7 @@ protected override void OnLoad(EventArgs e) {
 			try {
 				AppContext.Load(null);
 			}
-			catch (Exception ex) {
+			catch (Exception) {
 				// ignore loading exception
 			}
 			Text = Constants.AppName + " [" + Application.ProductVersion + "]";
@@ -557,7 +557,7 @@ void MainForm_FormClosed(object sender, FormClosedEventArgs e) {
 			try {
 				AppContext.Save(null, true);
 			}
-			catch (Exception ex) {
+			catch (Exception) {
 				// ignore error
 			}
 		}

App/Model/PdfInfoXmlDocument.cs

@@ -155,7 +155,7 @@ internal BookmarkRootElement(XmlDocument doc)
 	public sealed class BookmarkElement : BookmarkContainer
 	{
 		/// <summary>在自动生成书签时标记级别的属性。</summary>
-		internal int AutoLevel;
+		internal int AutoLevel = 0;
 
 		/// <summary>获取或设置书签的文本。</summary>
 		public string Title {

App/Model/SourceItem.cs

@@ -90,7 +90,7 @@ internal static SourceItem Create(FilePath path, bool refresh) {
 				catch (FileNotFoundException) {
 					FormHelper.ErrorBox(String.Concat("找不到文件：“", path, "”。"));
 				}
-				catch (Exception ex) {
+				catch (Exception) {
 					FormHelper.ErrorBox(String.Concat("打开 PDF 文件时“", path, "”出错。"));
 					// ignore corrupted 
 				}
@@ -279,7 +279,7 @@ private void Refresh(string path, Encoding encoding) {
 						PageRanges = new PageRange(1, PageCount).ToString();
 					}
 				}
-				catch (Exception ex) {
+				catch (Exception) {
 					FormHelper.ErrorBox(String.Concat("打开 PDF 文件时“", path, "”出错。"));
 					// ignore corrupted 
 				}
@@ -355,8 +355,8 @@ static void AddFiles(string folderPath, List<SourceItem> list) {
 						}
 					}
 				}
-				catch (UnauthorizedAccessException) {}
-				catch (IOException) {}
+				catch (UnauthorizedAccessException) { }
+				catch (IOException) { }
 			}
 
 			static void AddSubDirectories(string folderPath, List<SourceItem> list) {
@@ -366,8 +366,8 @@ static void AddSubDirectories(string folderPath, List<SourceItem> list) {
 						list.Add(f);
 					}
 				}
-				catch (UnauthorizedAccessException) {}
-				catch (IOException) {}
+				catch (UnauthorizedAccessException) { }
+				catch (IOException) { }
 			}
 		}
 

App/Processor/ContentProcessors/ReplaceFontProcessor.cs

@@ -53,7 +53,7 @@ public void BeginProcess(DocProcessorContext context) {
 				try {
 					_fontFactory.Register(item.Value, item.Key);
 				}
-				catch (Exception ex) {
+				catch (Exception) {
 					// ignore
 				}
 			}
@@ -334,7 +334,7 @@ void LoadFonts(PageProcessorContext context, PdfDictionary fonts) {
 							}
 							_newFonts.Add(n, nf);
 						}
-						catch (Exception ex) {
+						catch (Exception) {
 							Tracker.TraceMessage(Tracker.Category.Error, "无法加载字体");
 							throw;
 						}

App/Processor/ImageExtractor.cs

@@ -374,7 +374,7 @@ private void SaveBitmap(ImageInfo info, byte[] bytes, string fileName) {
 						try {
 							bmp.Save(n, FREE_IMAGE_FORMAT.FIF_PNG);
 						}
-						catch (System.Runtime.InteropServices.SEHException ex) {
+						catch (System.Runtime.InteropServices.SEHException) {
 							Tracker.TraceMessage(Tracker.Category.Error, "保存图片时出现错误，请联系程序开发者：" + n);
 						}
 					}

App/Processor/Imaging/JpgHelper.cs

@@ -49,7 +49,7 @@ internal static bool TryGetExifOrientation(string fileName, out ushort b) {
 					return r.GetTagValue(ExifTags.Orientation, out b);
 				}
 			}
-			catch (Exception ex) {
+			catch (Exception) {
 				b = 0;
 				return false;
 			}

App/Processor/OcrProcessor.cs

@@ -72,7 +72,7 @@ private static void CleanUpTempFiles(string folderPath) {
 				try {
 					File.Delete(file);
 				}
-				catch (Exception ex) {
+				catch (Exception) {
 				}
 			}
 		}

App/Processor/PdfProcessingEngine.cs

@@ -1,9 +1,7 @@
 using System;
 using System.Collections.Generic;
-using System.Text;
 using iTextSharp.text;
 using iTextSharp.text.pdf;
-using PDFPatcher.Model;
 
 namespace PDFPatcher.Processor
 {
@@ -119,7 +117,7 @@ internal void ProcessDocument(PdfWriter writer, Document document) {
 						pc.WritePageCommands();
 					}
 				}
-				catch (Exception ex) {
+				catch (Exception) {
 					Tracker.TraceMessage("在处理文档第 " + i + " 页时出错。");
 					throw;
 				}