From 42aed43d2dc19f6161837fe9ccfba1cdc44442be Mon Sep 17 00:00:00 2001
From: techniX <sergei.mozhaisky@gmail.com>
Date: Sun, 8 Dec 2019 22:35:14 +0200
Subject: [PATCH] transmitter: better formspec validation

---
 transmitter.lua | 31 +++++++++++++++++++++----------
 1 file changed, 21 insertions(+), 10 deletions(-)

diff --git a/transmitter.lua b/transmitter.lua
index dd81c1b..9f3ce77 100644
--- a/transmitter.lua
+++ b/transmitter.lua
@@ -66,18 +66,29 @@ minetest.register_node("ham_radio:transmitter", {
       return
     end
 
-    local is_frequency_valid = ham_radio.validate_frequency(fields.frequency)
-    if is_frequency_valid.result == false then
-      ham_radio.errormsg(sender, is_frequency_valid.message)
-      return
+    local meta = minetest.get_meta(pos)
+    local transmitter_is_updated = false
+
+    if fields.frequency ~= nil then
+      local is_frequency_valid = ham_radio.validate_frequency(fields.frequency)
+      if is_frequency_valid.result == false then
+        ham_radio.errormsg(sender, is_frequency_valid.message)
+      else
+        meta:set_string("frequency", fields.frequency)
+        transmitter_is_updated = true
+      end
     end
 
-    local meta = minetest.get_meta(pos)
-    meta:set_string("frequency", fields.frequency)
-    meta:set_string("rds_message", fields.rds_message)
-    ham_radio.transmitter_update_infotext(meta)
-    ham_radio.save_transmitter(pos, meta)
-    ham_radio.play_tuning_sound(sender)
+    if fields.rds_message ~= nil then
+      meta:set_string("rds_message", fields.rds_message)
+      transmitter_is_updated = true
+    end
+
+    if transmitter_is_updated then
+      ham_radio.transmitter_update_infotext(meta)
+      ham_radio.save_transmitter(pos, meta)
+      ham_radio.play_tuning_sound(sender)
+    end
   end,
   can_dig = function(pos,player)
     local meta = minetest.get_meta(pos);