fix usb-detection bug and update travis ci script

.travis.yml

@@ -47,12 +47,10 @@ before_install:
     /usr/bin/ruby -e "$(curl -fsSL https://raw.githubusercontent.com/Homebrew/install/master/install)";
     brew cask install arduino;
   fi
-
-install:
 - npm install -g vsce
-- npm install -g node-gyp
 - npm install -g typescript
-- npm install -g gulp
+
+install:
 - npm install
 # https://github.com/travis-ci/travis-ci/issues/8813
 - rm -f ./node_modules/.bin/which

package.json

@@ -564,6 +564,7 @@
     "gulp-typescript": "^5.0.1",
     "minimist": "^1.2.0",
     "mocha": "^6.2.2",
+    "node-gyp": "^6.1.0",
     "plugin-error": "^1.0.1",
     "tslint": "^5.20.1",
     "typemoq": "^1.6.0",
@@ -580,7 +581,7 @@
     "iconv-lite": "^0.4.18",
     "impor": "^0.1.1",
     "properties": "^1.2.1",
-    "usb-native": "^5.0.7",
+    "usb-native": "^5.0.12",
     "uuid": "^3.0.1",
     "vscode-extension-telemetry": "0.0.18",
     "winreg": "^1.2.3",

src/serialmonitor/usbDetector.ts

@@ -160,10 +160,13 @@ export class UsbDetector {
         }
     }
 
-    private showReadMeAndExample(readme: string) {
+    private showReadMeAndExample(readme: string|undefined) {
         if (ArduinoContext.boardManager.currentBoard) {
-            let readmeFilePath = path.join(ArduinoContext.boardManager.currentBoard.platform.rootBoardPath, readme);
-            if (!util.fileExistsSync(readmeFilePath)) {
+            let readmeFilePath = "";
+            if (readme) {
+                readmeFilePath = path.join(ArduinoContext.boardManager.currentBoard.platform.rootBoardPath, readme);
+            }
+            if (!readmeFilePath || !util.fileExistsSync(readmeFilePath)) {
                 readmeFilePath = path.join(ArduinoContext.boardManager.currentBoard.platform.rootBoardPath, "README.md");
             }
             vscode.commands.executeCommand("arduino.showExamples", true);