fix nullable fields

Author: xuorig

app/models/graph/types/person.rb

@@ -18,12 +18,12 @@ module Types
         " is a battle that occurs at the end of Star Wars episode IV: A New Hope.",
         property: :birth_year
 
-      field :eyeColor, !types.String,
+      field :eyeColor, types.String,
         "The eye color of this person. Will be \"unknown\" if not known or \"n/a\" if the person does not have an eye.",
         property: :eye_color
 
       field :gender, !GenderEnum, "​The gender of this person."
-      field :hairColor, !types.String,
+      field :hairColor, types.String,
         "The hair color of this person. Will be \"unknown\" if not known or \"n/a\" if the person does not have hair.",
         property: :hair_color
 

app/models/graph/types/starship.rb

@@ -34,7 +34,7 @@ module Types
       field :model, !types.String, "The model or official name of this starship. Such as \"T-65 X-wing\" or \"DS-1 Orbital Battle Station\"."
 
       field :manufacturer, !types.String, "The manufacturer of this starship."
-      field :costInCredits, !types.Float, "The cost of this starship new, in galactic credits", property: :cost_in_credits
+      field :costInCredits, types.Float, "The cost of this starship new, in galactic credits", property: :cost_in_credits
       field :length, !types.Float, "The length of this starship in meters."
       field :crew, !types.String, "The number of personnel needed to run or pilot this starship."
       field :passengers, !types.String, "The number of non-essential people this starship can transport."

app/models/graph/types/vehicle.rb

@@ -20,7 +20,7 @@ module Types
       field :model, !types.String, "The model or official name of this vehicle. Such as \"All-Terrain Attack Transport\"."
 
       field :manufacturer, !types.String, "The manufacturer of this vehicle."
-      field :costInCredits, !types.Float, "The cost of this vehicle new, in galactic credits", property: :cost_in_credits
+      field :costInCredits, types.Float, "The cost of this vehicle new, in galactic credits", property: :cost_in_credits
       field :length, !types.Float, "The length of this vehicle in meters."
       field :crew, !types.String, "The number of personnel needed to run or pilot this vehicle."
       field :passengers, !types.String, "The number of non-essential people this vehicle can transport."