prevent broken uploads that create files with 0 bytes

resolves: AndiDittrich#83

lib/connector/upload.js

@@ -5,8 +5,6 @@ const _luaCommandBuilder = require('../lua/command-builder');
 const _logger = require('logging-facility').getLogger('connector');
 const _luaMinifier = require('../lua/minifier');
 
-// hex write helper already uploaded within current session ?
-let _isTransferWriteHelperUploaded = false;
 let _transferEncoding = null;
 
 // utility function to handle the file transfer
@@ -85,34 +83,27 @@ async function startTransfer(rawContent, localName, remoteName, progressCb){
 
 // utility function to upload file transfer helper
 async function requireTransferHelper(){
-    // hex write helper already uploaded within current session ?
-    // otherwise upload helper
-    if (_isTransferWriteHelperUploaded !== true){
-        let response = null;
-
-        try{
-            ({response} = await _virtualTerminal.executeCommand(_luaCommandBuilder.command.transferWriteHelper));
-
-        }catch(e){
-            _logger.debug(e);
-            throw new Error('cannot upload transfer helper function');
-        }
+    let response = null;
 
-        // get transfer encoding
-        if (response == 'b'){
-            _transferEncoding = 'base64'
-        }else if (response == 'h'){
-            _transferEncoding = 'hex'
-        }else{
-            throw new Error('unknown transfer encoding - ' + response);
-        }
+    try{
+        ({response} = await _virtualTerminal.executeCommand(_luaCommandBuilder.command.transferWriteHelper));
 
-        // show encoding
-        _logger.log('Transfer-Mode: ' + _transferEncoding);
+    }catch(e){
+        _logger.debug(e);
+        throw new Error('cannot upload transfer helper function');
+    }
 
-        // set flag
-        _isTransferWriteHelperUploaded = true;
+    // get transfer encoding
+    if (response == 'b'){
+        _transferEncoding = 'base64'
+    }else if (response == 'h'){
+        _transferEncoding = 'hex'
+    }else{
+        throw new Error('unknown transfer encoding - ' + response);
     }
+
+    // show encoding
+    _logger.log('Transfer-Mode: ' + _transferEncoding);
 }
 
 async function upload(localName, remoteName, options, progressCb){