Loghistory: fixed error when an empty blob-field was logged

(cherry picked from commit 0c3a5968)

process/Loghistory_lib/process.js

@@ -346,7 +346,7 @@ LogHistoryExecutor.prototype._getFormattedValue = function (pColumnName, pDescri
     }
     else if (pDescription.translate4Log != null && pDescription.translate4Log != "") 
     {
-        var params = Translate4LogParams.generateParams(this.idValue, pValue.toString(), this.sqlAction, this.translationLanguage);
+        var params = Translate4LogParams.generateParams(this.idValue, pValue != null ? pValue.toString() : null, this.sqlAction, this.translationLanguage);
         var scriptId = "LogHistoryExecutor._getFormattedValue." 
             + this.structureDefinitionAlias + "." + this.affectedTable + "." +  pColumnName + ".translate4Log";
         pValue = process.executeScript(scriptId, pDescription.translate4Log, params, vars.get("$sys.dbalias"));