.github: PackageMatrix: Bugfix empty packages list

The list of packages in the generated matrix can sometimes be empty,
which is invalid and will result in the actual matrix of job runners
failing to generate (because all values must be a non-empty array).

This commit performs a final validation of job matrix, removing all
default configs if the package list is empty, and removing the includes
list if it is empty.

Author: Javagedes

.github/workflows/PackageMatrix.yml

@@ -76,7 +76,7 @@ jobs:
     runs-on: ubuntu-latest
 
     outputs:
-      matrix: ${{ steps.filter-matrix.outputs.matrix || steps.set-packages.outputs.matrix }}
+      matrix: ${{ steps.clean-matrix.outputs.matrix }}
 
     steps:
       - name: Checkout repository
@@ -171,3 +171,51 @@ jobs:
           echo "::endgroup::"
           echo ""
           echo "matrix=$OUTPUT" >> "$GITHUB_OUTPUT"
+
+      - name: Clean matrix if no packages found
+        if: always()
+        id: clean-matrix
+        shell: bash
+        env:
+          MATRIX: ${{ steps.filter-matrix.outputs.matrix || steps.set-packages.outputs.matrix }}
+          DEFAULT_CONFIG: ${{ inputs.default-config }}
+        run: |
+          echo "Checking if matrix has any packages..."
+          
+          # Check if packages array is empty
+          PACKAGES_COUNT=$(echo "$MATRIX" | jq '.packages | length')
+          
+          echo "Packages count: $PACKAGES_COUNT"
+          
+          if [ "$PACKAGES_COUNT" -eq 0 ]; then
+            echo "No packages found - removing default-config dimensions and packages, keeping include only"
+            # Keep only include, remove packages and all default-config dimensions
+            OUTPUT=$(echo "$MATRIX" | jq '{include: .include}')
+          else
+            echo "Packages found - keeping matrix as-is"
+            OUTPUT="$MATRIX"
+          fi
+          
+          # Remove include if it's an empty array (regardless of packages count)
+          INCLUDE_COUNT=$(echo "$OUTPUT" | jq '.include | length')
+          echo "Include count: $INCLUDE_COUNT"
+          
+          if [ "$INCLUDE_COUNT" -eq 0 ]; then
+            echo "Include array is empty - removing it"
+            OUTPUT=$(echo "$OUTPUT" | jq 'del(.include)')
+          fi
+          
+          # Check if we have an empty JSON object and return empty string instead
+          OBJECT_KEYS=$(echo "$OUTPUT" | jq 'keys | length')
+          if [ "$OBJECT_KEYS" -eq 0 ]; then
+            echo "Matrix is completely empty - returning empty string"
+            OUTPUT=''
+          fi
+          
+          echo "::group::Final matrix JSON"
+          echo "$OUTPUT" | jq .
+          echo "::endgroup::"
+          echo ""
+          # Ensure compact JSON output for GitHub Actions
+          COMPACT_OUTPUT=$(echo "$OUTPUT" | jq -c .)
+          echo "matrix=$COMPACT_OUTPUT" >> "$GITHUB_OUTPUT"