tiny cleanup in shell for crashed scripts

remove unknown error message

src/main/resources/assets/opencomputers/loot/openos/bin/sh.lua

@@ -5,6 +5,8 @@ local sh = require("sh")
 
 local args = shell.parse(...)
 
+local t = type
+
 shell.prime()
 
 if #args == 0 then
@@ -19,6 +21,7 @@ if #args == 0 then
       if tty.getCursor() > 1 then
         io.write("\n")
       end
+      io.write("type:", t(type), '\n')
       io.write(sh.expand(os.getenv("PS1") or "$ "))
     end
     tty.window.cursor = input_handler
@@ -31,8 +34,8 @@ if #args == 0 then
       elseif command ~= "" then
         --luacheck: globals _ENV
         local result, reason = sh.execute(_ENV, command)
-        if not result then
-          io.stderr:write((reason and tostring(reason) or "unknown error") .. "\n")
+        if not result and reason then
+          io.stderr:write(tostring(reason), "\n")
         end
       end
     elseif command == nil then -- false only means the input was interrupted

src/main/resources/assets/opencomputers/loot/openos/lib/sh.lua

@@ -198,7 +198,7 @@ function sh.execute(env, command, ...)
   if type(words) ~= "table" then
     return words, reason
   elseif #words == 0 then
-    return true, 0
+    return true
   end
 
   -- MUST be table.pack for non contiguous ...