Merge branch 'develop_PDFReaderProV4.6.0' of git.kdan.cc:Mac_PDF/PDF_Office into develop_PDFReaderProV4.6.0

PDF Office/PDF Master/Class/PDFTools/TTS/WindowController/KMTTSWindowController.swift

@@ -338,7 +338,9 @@ class KMTTSWindowController: NSWindowController, KMTTSManagerDelegate, NSWindowD
             } else {
                 let page = self.pdfView.currentPage()
                 self.currentPageIndex = self.pdfView.currentPageIndex
-                self.startSpeakingPDFPage(page!)
+                if page != nil {
+                    self.startSpeakingPDFPage(page!)
+                }
             }
         }
     }