more THEMERM and THEMERMFILL

Give a little more information if environment variable THEMERM or
THEMERMFILL has an invalid value.

dat/themerms.lua

@@ -982,15 +982,22 @@ end
 function pre_themerooms_generate()
    local debug_themerm = nh.debug_themerm(false)
    local debug_fill = nh.debug_themerm(true)
+   local xtrainfo = ""
    debug_rm_idx = lookup_by_name(debug_themerm, false)
    debug_fill_idx = lookup_by_name(debug_fill, true)
    if debug_themerm ~= nil and debug_rm_idx == nil then
+      if lookup_by_name(debug_themerm, true) ~= nil then
+         xtrainfo = "; it is a fill type"
+      end
       pline("Warning: themeroom '"..debug_themerm
-            .."' not found in themerooms", true)
+            .."' not found in themerooms"..xtrainfo, true)
    end
    if debug_fill ~= nil and debug_fill_idx == nil then
+      if lookup_by_name(debug_fill, false) ~= nil then
+         xtrainfo = "; it is a room type"
+      end
       pline("Warning: themeroom fill '"..debug_fill
-            .."' not found in themeroom_fills", true)
+            .."' not found in themeroom_fills"..xtrainfo, true)
    end
 end
 

src/nhlua.c

@@ -990,7 +990,7 @@ nhl_get_debug_themerm_name(lua_State *L)
         lua_pop(L, 1);
         if (wizard)
             dbg_themerm = getenv(is_fill ? "THEMERMFILL" : "THEMERM");
-        if (!dbg_themerm || strlen(dbg_themerm) == 0) {
+        if (!dbg_themerm || !*dbg_themerm) {
             lua_pushnil(L);
         } else {
             lua_pushstring(L, dbg_themerm);