gradle: handle missing release version in dependencies

                  uniqueVersions' = map (x: x.version) uniqueVersionFiles;

                  releaseVersions = map (x: x.version) (builtins.filter (x: !x.isSnapshot) uniqueVersionFiles);

                  latestVer = v.latest or v.release or (lib.last uniqueVersions');

                  releaseVer = v.release or (lib.last releaseVersions);

                  releaseVer = v.release or (if releaseVersions != [ ] then lib.last releaseVersions else null);

                  # The very latest version isn't necessarily used by Gradle, so it may not be present in the MITM data.

                  # In order to generate better metadata xml, if the latest version is known but wasn't fetched by Gradle,

                  # add it anyway.

                  uniqueVersions =

                    uniqueVersions'

                    ++ lib.optional (!builtins.elem releaseVer uniqueVersions') releaseVer

                    ++ lib.optional (releaseVer != null && !builtins.elem releaseVer uniqueVersions') releaseVer

                    ++ lib.optional (!builtins.elem latestVer uniqueVersions' && releaseVer != latestVer) latestVer;

                  lastUpdated =

                  ''

                else

                  assert !containsSpecialXmlChars latestVer;

                  assert !containsSpecialXmlChars releaseVer;

                  assert releaseVer == null || !containsSpecialXmlChars releaseVer;

                  ''

                    <?xml version="1.0" encoding="UTF-8"?>

                    <metadata modelVersion="1.1.0">

                      <artifactId>${artifactId}</artifactId>

                      <versioning>

                        <latest>${latestVer}</latest>

                        <release>${releaseVer}</release>

                    ${lib.optionalString (releaseVer != null) "    <release>${releaseVer}</release>"}

                        <versions>

                    ${builtins.concatStringsSep "\n" (map (x: "      <version>${x}</version>") uniqueVersions)}

                        </versions>