tdf#97831 follow up : remove unused arguments from stack

Intention:
Make e.g. [1+SWITCH(1;1;1;6)] work. Without this fix, the result is
7 but should be 2.

Change-Id: I2a72e458e5458c02c3ce2f4214b86ba13f7b1d11
Reviewed-on: https://gerrit.libreoffice.org/27664Tested-by: Jenkins <ci@libreoffice.org>
Reviewed-by: Eike Rathke <erack@redhat.com>
Tested-by: Eike Rathke <erack@redhat.com>

sc/source/core/tool/interpr8.cxx

@@ -1897,7 +1897,15 @@ void ScInterpreter::ScIfs_MS()
     //push result :
     FormulaTokenRef xToken( PopToken() );
     if ( xToken )
+    {
+        // Remove unused arguments of IFS from the stack before pushing the result.
+        while ( nParamCount > 1 )
+        {
+            Pop();
+            nParamCount--;
+        }
         PushTempToken( xToken.get() );
+    }
     else
         PushError( errUnknownStackVariable );
 }
@@ -2000,7 +2008,15 @@ void ScInterpreter::ScSwitch_MS()
     // push result
     FormulaTokenRef xToken( PopToken() );
     if ( xToken )
+    {
+        // Remove unused arguments of SWITCH from the stack before pushing the result.
+        while ( nParamCount > 1 )
+        {
+            Pop();
+            nParamCount--;
+        }
         PushTempToken( xToken.get() );
+    }
     else
         PushError( errUnknownStackVariable );
 }