tdf#154285 Check too many arguments to BASIC FILELEN function

Change-Id: I21704e84bed54ad4295d52d82eb4a92ff70a3abc
Reviewed-on: https://gerrit.libreoffice.org/c/core/+/201298
Tested-by: Jenkins
Reviewed-by: Mike Kaganski <mike.kaganski@collabora.com>

basic/source/runtime/methods.cxx

@@ -708,7 +708,7 @@ void SbRtl_Exp(StarBASIC *, SbxArray & rPar, bool)
 
 void SbRtl_FileLen(StarBASIC *, SbxArray & rPar, bool)
 {
-    if (rPar.Count() < 2)
+    if (rPar.Count() != 2)
     {
         return StarBASIC::Error( ERRCODE_BASIC_BAD_ARGUMENT );
     }