tdf#154285 Check argument count in BASIC SGN function

Change-Id: Ic20ceed1d736ea2436bc4dd37cfd242efcec79b4
Reviewed-on: https://gerrit.libreoffice.org/c/core/+/206268
Tested-by: Jenkins
Reviewed-by: Ilmari Lauhakangas <ilmari.lauhakangas@libreoffice.org>

basic/source/runtime/methods.cxx

@@ -1273,7 +1273,7 @@ void SbRtl_RTrim(StarBASIC *, SbxArray & rPar, bool)
 
 void SbRtl_Sgn(StarBASIC *, SbxArray & rPar, bool)
 {
-    if (rPar.Count() < 2)
+    if (rPar.Count() != 2)
         return StarBASIC::Error( ERRCODE_BASIC_BAD_ARGUMENT );
 
     double aDouble = rPar.Get(1)->GetDouble();