Fixed Nvm Source Issue(#1078) (#1114)

* Fixed Nvm Source Issue

* Fix: Test Scenario Failure

* Updated node feature version

* Incorporated Review Comment

src/node/devcontainer-feature.json

 {
     "id": "node",
-    "version": "1.6.0",
+    "version": "1.6.1",
     "name": "Node.js (via nvm), yarn and pnpm",
     "documentationURL": "https://github.com/devcontainers/features/tree/main/src/node",
     "description": "Installs Node.js, nvm, yarn, pnpm, and needed dependencies.",

src/node/install.sh

@@ -227,7 +227,7 @@ install_yarn() {
                 # Yum/DNF want to install nodejs dependencies, we'll use NPM to install yarn
                 su ${USERNAME} -c "umask 0002 && . '${NVM_DIR}/nvm.sh' && nvm use ${_ver} && npm install --global yarn"
             fi
-        else 
+        else
             echo "Yarn already installed."
         fi
     fi
@@ -309,7 +309,7 @@ curl -so- "https://raw.githubusercontent.com/nvm-sh/nvm/v${NVM_VERSION}/install.
     curl -so- "https://raw.githubusercontent.com/nvm-sh/nvm/\${PREV_NVM_VERSION}/install.sh" | bash
     NVM_VERSION="\${PREV_NVM_VERSION}"
 }
-source "${NVM_DIR}/nvm.sh"
+[ -s "${NVM_DIR}/nvm.sh" ] && source "${NVM_DIR}/nvm.sh"
 if [ "${NODE_VERSION}" != "" ]; then
     nvm alias default "${NODE_VERSION}"
 fi