correct type issues

src/Model/Global/fileTransferModel.ts

@@ -37,6 +37,7 @@ export default class FileTransferModel {
     };
 
     readonly prepareToSend = (): void => {
+	if (!this.transferData) return;
         this.direction = TransferDirections.Send;
         this.connectionModel.addChannel(this.transferData.channel);
     };
@@ -156,7 +157,7 @@ export default class FileTransferModel {
     };
 
     readonly prepareFileForSending = (filePath: string[]): string => {
-        const fileContent: string | undefined =
+        const fileContent: string | null =
             this.storageModel.read(filePath);
         if (fileContent == null) return "";
 
@@ -168,6 +169,8 @@ export default class FileTransferModel {
     };
 
     readonly sendFile = async (stringifiedFileData: string): Promise<void> => {
+	if (!this.transferData) return;
+
         const encryptedFileData: string = await encryptString(
             stringifiedFileData,
             this.transferData.key,