Update lua-env.lua

src/lua-env.lua

@@ -18,6 +18,8 @@ end
 
 -- Called when pcall fails on a ts->lua call, used to print detailed error info
 function _bllua_on_error(err)
+  -- Convert error to string if it's not already
+  err = tostring(err)
   err = err:match(': (.+)$') or err
   local tracelines = { err }
   local level = 2
@@ -25,7 +27,7 @@ function _bllua_on_error(err)
     local info = debug.getinfo(level)
     if not info then break end
     local filename = debug.getfilename(level) or info.short_src
-    local funcname = info.name
+    local funcname = info.name or '<unknown>'
     if funcname == 'dofile' then break end
     table.insert(tracelines, string.format('%s:%s in function \'%s\'',
       filename,