Fixes CI problem for forks (#540)

Fixing CI problem for forks by setting default values and handling empty
secrets

.github/actions/docker-build/action.yml

@@ -31,7 +31,15 @@ runs:
     - name: NGC Login
       shell: sh
       run: |
+        # Only attempt NGC login if API key is available
+        if [ -n "${{ env.NGC_API_KEY }}" ]; then
+          echo "Logging into NGC registry..."
           docker login -u \$oauthtoken -p ${{ env.NGC_API_KEY }} nvcr.io
+          echo "✅ Successfully logged into NGC registry"
+        else
+          echo "⚠️ NGC_API_KEY not available - skipping NGC login"
+          echo "This is normal for PRs from forks or when secrets are not configured"
+        fi
 
     - name: Build Docker Image
       shell: sh

.github/workflows/build.yml

@@ -23,8 +23,8 @@ permissions:
 
 env:
   NGC_API_KEY: ${{ secrets.NGC_API_KEY }}
-  ISAACSIM_BASE_IMAGE: ${{ vars.ISAACSIM_BASE_IMAGE }}
-  ISAACSIM_BASE_VERSION: ${{ vars.ISAACSIM_BASE_VERSION }}
+  ISAACSIM_BASE_IMAGE: ${{ vars.ISAACSIM_BASE_IMAGE || 'nvcr.io/nvidia/isaac-sim' }}
+  ISAACSIM_BASE_VERSION: ${{ vars.ISAACSIM_BASE_VERSION || '4.5.0' }}
   DOCKER_IMAGE_TAG: isaac-lab-dev:${{ github.event_name == 'pull_request' && format('pr-{0}', github.event.pull_request.number) || github.ref_name }}-${{ github.sha }}
 
 jobs:
@@ -52,7 +52,7 @@ jobs:
         git lfs install
 
     - name: Checkout Code
-      uses: actions/checkout@v3
+      uses: actions/checkout@v4
       with:
         fetch-depth: 0
         lfs: true
@@ -114,7 +114,7 @@ jobs:
         git lfs install
 
     - name: Checkout Code
-      uses: actions/checkout@v3
+      uses: actions/checkout@v4
       with:
         fetch-depth: 0
         lfs: true
@@ -172,7 +172,7 @@ jobs:
         git lfs install
 
     - name: Checkout Code
-      uses: actions/checkout@v3
+      uses: actions/checkout@v4
       with:
         fetch-depth: 0
         lfs: false

.github/workflows/postmerge-ci.yml

@@ -45,7 +45,15 @@ jobs:
 
     - name: Login to NGC
       run: |
+        # Only attempt NGC login if API key is available
+        if [ -n "${{ env.NGC_API_KEY }}" ]; then
+          echo "Logging into NGC registry..."
           docker login -u \$oauthtoken -p ${{ env.NGC_API_KEY }} nvcr.io
+          echo "✅ Successfully logged into NGC registry"
+        else
+          echo "⚠️ NGC_API_KEY not available - skipping NGC login"
+          echo "This is normal when secrets are not configured"
+        fi
 
     - name: Build and Push Docker Images
       run: |