Silence various undeclared variable warnings

scaffold:

    2021-08-18 22:42:54: WARNING[Main]: Assignment to undeclared global "sdir" inside a function at scaffold:/railscaffold.lua:151.

incrementaltp:  Fix this by adding `optional_depends` to `mod.conf`

2021-08-18 22:52:39: WARNING[Main]: Undeclared global variable "autofly" accessed at incrementaltp:init.lua:85
2021-08-18 22:52:39: WARNING[Main]: Undeclared global variable "autofly" accessed at incrementaltp:init.lua:87

dte:

2021-08-18 22:59:26: WARNING[Main]: Assignment to undeclared global "_" inside a function at dte:init.lua:375.

tchat:  Use `get_modpath('wisp')` to fix this

2021-08-18 23:21:20: WARNING[Main]: Undeclared global variable "wisp" accessed at tchat:init.lua:537

clientmods/dte/init.lua

@@ -372,6 +372,7 @@ end
 local function load_UI(name)  -- open/create a ui file
     current_ui_file = name
     modstorage:set_string("_GUI_editor_selected_file", current_ui_file)
+    local _
     _, widgets = pcall(loadstring("return "..modstorage:get_string("_GUI_editor_file_"..current_ui_file)))
     if widgets == nil then
         widgets = {{type="Display", name="", width=5, height=5, width_param=false, height_param=false, left=0.5, top=0.5,

clientmods/incrementaltp/mod.conf

@@ -0,0 +1,4 @@
+name = incrementaltp
+author = cora
+description = Teleport to a destination in increments
+optional_depends = autofly

clientmods/scaffold/railscaffold.lua

@@ -148,7 +148,7 @@ end,function() --stopfunc
 end,{'afly_axissnap','continuous_forward','autorefill'}) --'scaffold_ltbm'
 
 ws.on_connect(function()
-        sdir=storage:get_string('BOTDIR')
+        local sdir=storage:get_string('BOTDIR')
         if sdir ~= "" then
             ws.set_dir(sdir)
         else

clientmods/tchat/init.lua

@@ -130,6 +130,9 @@ local message_to = minetest.settings:get("tchat_prefix_send")
 local team_mode = minetest.settings:get_bool("tchat_team_mode")
 
 local use_wisp = minetest.settings:get_bool("tchat_use_wisp")
+if minetest.get_modpath('wisp') == nil then
+   use_wisp = false
+end
 
 local hide_sent = minetest.settings:get_bool("tchat_hide_sent")
 local blacklist = string.split(minetest.settings:get("tchat_blacklist"))
@@ -320,7 +323,7 @@ end
 
 
 local function dm(player, message)
-    if wisp == nil or not use_wisp then
+    if not use_wisp then
         minetest.send_chat_message("/msg " .. player .." " .. message)
     else
         wisp.send(player, message, true)
@@ -534,7 +537,7 @@ table.insert(minetest.registered_on_receiving_chat_message, 1, function(message)
     end
 end)
 
-if wisp ~= nil then
+if use_wisp then
     wisp.register_on_receive_split(function(player, message)
         if message:find(message_prefix) then
             tchat.chat_append("E " .. player .. ": " .. clean_message(message))

clientmods/tchat/mod.conf

@@ -1,3 +1,4 @@
 name = tchat
 author = cora, system32
 description = Adds a team chat and prevents accidental sending of coordinates. Supports Wisp for encrypting messages.
+optional_depends = wisp