CI(Docker): Fix failures in forks when fetching latest tag or current branch fails (OSGeo#6506)

Author: echoix

.github/workflows/docker.yml

@@ -84,25 +84,40 @@ jobs:
           latest_tag="$(git tag --sort=-v:refname \
             | grep -E '^[0-9]+\.[0-9]+\.[0-9]+$' \
             | head -n 1)"
-          latest_rel_branch="$(git branch --all --list 'origin/*' \
-            --contains "${latest_tag}" --format "%(refname:lstrip=3)")"
           echo "latest_tag=${latest_tag}" >> "${GITHUB_OUTPUT}"
           echo "latest_tag is: ${latest_tag}"
+          if [ -z "$latest_tag" ]; then
+              echo "Error getting latest tag information"
+              echo "error_latest=yes" >> "${GITHUB_OUTPUT}"
+              exit 0
+          fi
+          latest_rel_branch="$(git branch --all --list 'origin/*' \
+            --contains "${latest_tag}" --format "%(refname:lstrip=3)" || echo "")"
           echo "latest_rel_branch=${latest_rel_branch}" >> "${GITHUB_OUTPUT}"
           echo "latest_rel_branch is: ${latest_rel_branch}"
+          if [ -z "$latest_rel_branch" ]; then
+              echo "Error getting latest release branch information"
+              echo "error_latest_rel_branch=yes" >> "${GITHUB_OUTPUT}"
+              exit 0
+          fi
+          echo "error_latest=no" >> "${GITHUB_OUTPUT}"
+          echo "error_latest_rel_branch=no" >> "${GITHUB_OUTPUT}"
       - name: Get enable values for meta step
         id: enable
         run: |
           latest="${{
             (github.ref || format('{0}{1}', 'refs/tags/', github.event.release.tag_name))
               == format('refs/tags/{0}', steps.tag-branch.outputs.latest_tag)
-            && matrix.os == 'ubuntu' }}"
+            && matrix.os == 'ubuntu' && steps.tag-branch.outputs.error_latest == 'no' }}"
           current="${{
             ( contains(fromJSON('["tag", "release"]'), github.event_name)
               && (github.ref || format('{0}{1}', 'refs/tags/', github.event.release.tag_name))
                   == format('refs/tags/{0}', steps.tag-branch.outputs.latest_tag)
             )
-            || github.ref == format('refs/heads/{0}', steps.tag-branch.outputs.latest_rel_branch)
+            || ( github.ref == format('refs/heads/{0}', steps.tag-branch.outputs.latest_rel_branch)
+                  && steps.tag-branch.outputs.error_latest == 'no'
+                  && steps.tag-branch.outputs.error_latest_rel_branch == 'no'
+                )
           }}"
           echo "latest=${latest}" >> "${GITHUB_OUTPUT}"
           echo "latest is ${latest}"