improve error message

Change-Id: Id1408cb1d8f04b36ffab65b684a94b14db9d9c50
diff --git a/editeng/source/uno/unoipset.cxx b/editeng/source/uno/unoipset.cxx
index 3fd6de0..f325079 100644
--- a/editeng/source/uno/unoipset.cxx
+++ b/editeng/source/uno/unoipset.cxx
@@ -302,7 +302,7 @@ void SvxUnoConvertToMM( const SfxMapUnit eSourceMapUnit, uno::Any & rMetric ) th
                rMetric <<= (sal_uInt32)(TWIPS_TO_MM(*o3tl::forceAccess<sal_uInt32>(rMetric)));
                break;
            default:
                OSL_FAIL("AW: Missing unit translation to 100th mm!");
                OSL_FAIL(OString("AW: Missing unit translation to 100th mm, " + OString::number(rMetric.getValueTypeClass())).getStr());
            }
            break;
        }