random gen to fill given term

src/GF/Shell.hs

@@ -173,15 +173,17 @@ execC co@(comm, opts0) sa@((st,(h,_)),a) = case comm of
   CTranslate il ol -> do
     let a' = opST2CommandArg (optParseArgErr opts (sgr il)) a
     returnArg (opTS2CommandArg (optLinearizeTreeVal opts (sgr ol)) a') sa
-  CGenerateRandom n -> case a of
-      ASTrm _ -> do
-        case s2t a of
-          ATrms [trm] -> do 
+  CGenerateRandom n -> do
+    let 
+      a' = case a of
+        ASTrm _ -> s2t a
+        _ -> a
+    case a' of
+      ATrms (trm:_) -> do
             g    <- newStdGen
             case (goFirstMeta (tree2loc trm) >>= refineRandom g 41 cgr) of
               Ok trm' -> returnArg (ATrms [loc2tree trm']) sa
               Bad s   -> returnArg (AError s) sa
-          _ -> returnArg a sa
       _ -> do
         ts <- randomTreesIO opts gro (optIntOrN opts flagNumber n)
         returnArg (ATrms ts) sa