Fix crash with too large clipboard data

If too much text is copied in the session, String.fromCharCode.apply()
would crash in Safari on macOS and Chrome on Linux. This commit fixes
this issue by avoiding apply() altogether. Also added test to cover this
issue.

kasmweb/core/rfb.js

@@ -1674,7 +1674,11 @@ export default class RFB extends EventTargetMixin {
                 streamInflator.setInput(null);
 
                 if (textData !== null) {
-                    textData = String.fromCharCode.apply(null, textData);
+                    let tmpText = "";
+                    for (let i = 0; i < textData.length; i++) {
+                        tmpText += String.fromCharCode(textData[i]);
+                    }
+                    textData = tmpText;
 
                     textData = decodeUTF8(textData);
                     if ((textData.length > 0) && "\0" === textData.charAt(textData.length - 1)) {

kasmweb/tests/test.rfb.js

@@ -2514,6 +2514,38 @@ describe('Remote Frame Buffer Protocol Client', function () {
                         client.removeEventListener("clipboard", spy);
                     });
 
+                    it('should be able to handle large Provide messages', function () {
+                        // repeat() is not supported in IE so a loop is needed instead
+                        let expectedData = "hello";
+                        for (let i = 1; i <= 100000; i++) {
+                            expectedData += "hello";
+                        }
+
+                        let data = [3, 0, 0, 0];
+                        const flags = [0x10, 0x00, 0x00, 0x01];
+
+                        let text = encodeUTF8(expectedData + "\0");
+
+                        let deflatedText = deflateWithSize(text);
+
+                        // How much data we are sending.
+                        push32(data, toUnsigned32bit(-(4 + deflatedText.length)));
+
+                        data = data.concat(flags);
+
+                        let sendData = new Uint8Array(data.length + deflatedText.length);
+                        sendData.set(data);
+                        sendData.set(deflatedText, data.length);
+
+                        const spy = sinon.spy();
+                        client.addEventListener("clipboard", spy);
+
+                        client._sock._websocket._receive_data(sendData);
+                        expect(spy).to.have.been.calledOnce;
+                        expect(spy.args[0][0].detail.text).to.equal(expectedData);
+                        client.removeEventListener("clipboard", spy);
+                    });
+
                 });
 
                 describe('Handle Notify', function () {