Add party validation and inverse to GridObject associations

app/models/grid_character.rb

@@ -1,7 +1,10 @@
 # frozen_string_literal: true
 
 class GridCharacter < ApplicationRecord
-  belongs_to :party
+  belongs_to :party,
+             counter_cache: :weapons_count,
+             inverse_of: :characters
+  validates_presence_of :party
 
   validate :awakening_level, on: :update
   validate :transcendence, on: :update

app/models/grid_summon.rb

@@ -1,7 +1,10 @@
 # frozen_string_literal: true
 
 class GridSummon < ApplicationRecord
-  belongs_to :party
+  belongs_to :party,
+             counter_cache: :weapons_count,
+             inverse_of: :summons
+  validates_presence_of :party
 
   def summon
     Summon.find(summon_id)

app/models/grid_weapon.rb

@@ -2,7 +2,9 @@
 
 class GridWeapon < ApplicationRecord
   belongs_to :party,
-             counter_cache: :weapons_count
+             counter_cache: :weapons_count,
+             inverse_of: :weapons
+  validates_presence_of :party
 
   belongs_to :weapon_key1, class_name: 'WeaponKey', foreign_key: :weapon_key1_id, optional: true
   belongs_to :weapon_key2, class_name: 'WeaponKey', foreign_key: :weapon_key2_id, optional: true
@@ -29,6 +31,8 @@ class GridWeapon < ApplicationRecord
     return unless weapon.limit
 
     party.weapons.find do |party_weapon|
+      return unless party_weapon.id
+
       id_match = weapon.id == party_weapon.id
       series_match = weapon.series == party_weapon.weapon.series
       both_opus_or_draconic = weapon.opus_or_draconic? && party_weapon.weapon.opus_or_draconic?