Remove some unused assignments

Mainly to keep eslint happy with its new recommended rules. But it also
makes the code more clear to not have unused stuff in it.

The des code got a bit more refactoring since eslint was upset about the
final "i++" as it was technically an unused assignment.

app/ui.js

@@ -138,10 +138,8 @@ const UI = {
 
         let autoconnect = UI.getSetting('autoconnect');
         if (autoconnect === 'true' || autoconnect == '1') {
-            autoconnect = true;
             UI.connect();
         } else {
-            autoconnect = false;
             // Show the connect panel on first load unless autoconnecting
             UI.openConnectPanel();
         }
@@ -1213,7 +1211,7 @@ const UI = {
     },
 
     securityFailed(e) {
-        let msg = "";
+        let msg;
         // On security failures we might get a string with a reason
         // directly from the server. Note that we can't control if
         // this string is translated or not.

core/crypto/des.js

@@ -181,11 +181,11 @@ class DES {
     // Encrypt 8 bytes of text
     enc8(text) {
         const b = text.slice();
-        let i = 0, l, r, x; // left, right, accumulator
+        let l, r, x; // left, right, accumulator
 
         // Squash 8 bytes to 2 ints
-        l = b[i++]<<24 | b[i++]<<16 | b[i++]<<8 | b[i++];
-        r = b[i++]<<24 | b[i++]<<16 | b[i++]<<8 | b[i++];
+        l = b[0]<<24 | b[1]<<16 | b[2]<<8 | b[3];
+        r = b[4]<<24 | b[5]<<16 | b[6]<<8 | b[7];
 
         x = ((l >>> 4) ^ r) & 0x0f0f0f0f;
         r ^= x;
@@ -252,7 +252,7 @@ class DES {
 
         // Spread ints to bytes
         x = [r, l];
-        for (i = 0; i < 8; i++) {
+        for (let i = 0; i < 8; i++) {
             b[i] = (x[i>>>2] >>> (8 * (3 - (i % 4)))) % 256;
             if (b[i] < 0) { b[i] += 256; } // unsigned
         }

core/decoders/zrle.js

@@ -175,7 +175,7 @@ export default class ZRLEDecoder {
 
     _readRLELength() {
         let length = 0;
-        let current = 0;
+        let current;
         do {
             current = this._inflator.inflate(1)[0];
             length += current;

core/rfb.js

@@ -2949,7 +2949,7 @@ export default class RFB extends EventTargetMixin {
 
         // We need to handle errors when we requested the resize.
         if (this._FBU.x === 1 && this._FBU.y !== 0) {
-            let msg = "";
+            let msg;
             // The y-position indicates the status code from the server
             switch (this._FBU.y) {
                 case 1: