u_vitamin enchantment conditions do not work

[Standing-Storm]

Describe the bug

Trying to make an enchantment affected by levels of a custom vitamin and it was behaving very strangely. Checking the same with with the iron base-game vitamin, enchantment conditions appear to not work with it.

Attach save file

Pennyhill-trimmed.tar.gz

Steps to reproduce

Copying the following JSON somewhere into your game so it loads:

{ "type": "mutation", "id": "TEST_MUTATION_IRON", "name": { "str": "The testing mutation." }, "points": 0, "description": "The iron in your blood makes you super strong.", "starting_trait": false, "purifiable": false, "valid": false, "enchantments": [ { "condition": { "math": [ "u_vitamin('iron')", ">=", "0" ] }, "values": [ { "value": "STRENGTH", "add": 25 } ] } ]}

2. Load game
3. Check needs. Notice that your iron is -5
4. Check Strength. It's 33, meaning the enchantment above is working even though it should only work when iron is greater than 0.

Expected behavior

u_vitamin works with enchantment conditions

Screenshots

Versions and configuration

• OS: Windows
  • OS Version: 10.0.22621.3737 (22H2)
• Game Version: 7f60041 [64-bit]
• Graphics Version: Tiles
• Game Language: English [en]
• Mods loaded: [
  Dark Days Ahead [dda],
  Disable NPC Needs [no_npc_food],
  Portal Storms Ignore NPCs [personal_portal_storms],
  Slowdown Fungal Growth [no_fungal_growth]
  ]

Additional context

Check #74921 for what I was trying to do

[andrei8l]

/confirmed talker infrastructure is being bad again

diff --git a/src/math_parser_diag.cpp b/src/math_parser_diag.cpp
index 11de324929..693d46ad53 100644
--- a/src/math_parser_diag.cpp
+++ b/src/math_parser_diag.cpp
@@ -1464,11 +1464,11 @@ std::function<double( dialogue & )> vitamin_eval( char scope,
         std::vector<diag_value> const &params, diag_kwargs const &/* kwargs */ )
 {
     return[beta = is_beta( scope ), id = params[0]]( dialogue const & d ) {
-        if( d.actor( beta )->get_character() ) {
-            return static_cast<talker const *>( d.actor( beta ) )
-                   ->get_character()
-                   ->vitamin_get( vitamin_id( id.str( d ) ) );
+        talker const *const actor = d.actor( beta );
+        if( Character const *const chr = actor->get_character(); chr != nullptr ) {
+            return chr->vitamin_get( vitamin_id( id.str( d ) ) );
         }
+        debugmsg( "Tried to access vitamins of a non-Character talker" );
         return 0;
     };
 }

(ie. static cast the talker for the if check too)

vision_range() needs the same treatment.