msa: forbid nJ=1

pub/lib/manip.cpp

@@ -468,6 +468,8 @@ void NManip::slices_rebin()
     static string jSel = "";
     JSelAsk( "Start groups at spectra", JSel );
     while ( ROlo fin = fiter.get() ) {
+        if( fin->nJ()<=1 )
+            throw S("Only one slice in file");
         ROld fd = R2D( fin );
         ROlc fc = R2C( fin );
         POlo fout( fin->new_olo() );