HPCC-18966 Address invalid unsigned comparison

- Fixes invalid if less-than zero comparison on an unsigned

Signed-off-by: Rodrigo Pastrana <rodrigo.pastrana@lexisnexis.com>

esp/services/ws_sql/SQL2ECL/SQLExpression.cpp

@@ -552,7 +552,7 @@ void SQLBinaryExpression::toECLStringTranslateSource(
         }
 
     }
-    else if (translation1.length()<0 && translation2.length()<0)
+    else if (translation1.length() == 0 && translation2.length() == 0)
     {
         return;
     }