Separate the horn and magic checks

src/main/java/com/minelittlepony/client/model/components/ModelPonyHead.java

@@ -53,7 +53,7 @@ public class ModelPonyHead extends SkullOverlayEntityModel implements ICapitated
 
         super.render(move, swing, ticks, headYaw, headPitch, scale);
 
-        if (metadata.hasMagic()) {
+        if (metadata.hasHorn()) {
             getHead().applyTransform(scale);
             horn.renderPart(scale, null);
         }

src/main/java/com/minelittlepony/client/model/races/ModelUnicorn.java

@@ -86,10 +86,10 @@ public class ModelUnicorn<T extends LivingEntity> extends ModelEarthPony<T> impl
     protected void renderHead(float scale) {
         super.renderHead(scale);
 
-        if (canCast()) {
+        if (hasHorn()) {
             head.applyTransform(scale);
             horn.renderPart(scale, attributes.interpolatorId);
-            if (isCasting()) {
+            if (canCast() && isCasting()) {
                 horn.renderMagic(getMagicColor(), scale);
             }
         }

src/main/java/com/minelittlepony/client/pony/PonyData.java

@@ -122,9 +122,14 @@ public class PonyData implements IPonyData {
         return glowColor;
     }
 
+    @Override
+    public boolean hasHorn() {
+        return getRace() != null && getRace().getEffectiveRace(false).hasHorn();
+    }
+
     @Override
     public boolean hasMagic() {
-        return getRace() != null && getRace().getEffectiveRace(false).hasHorn() && getGlowColor() != 0;
+        return hasHorn() && getGlowColor() != 0;
     }
 
     @Override

src/main/java/com/minelittlepony/model/IUnicorn.java

@@ -15,6 +15,13 @@ public interface IUnicorn<ArmModel> extends IModel {
         return getMetadata().hasMagic();
     }
 
+    /**
+     * Returns true if this model has an visible horns.
+     */
+    default boolean hasHorn() {
+        return getMetadata().hasHorn();
+    }
+
     /**
      * Returns true if this model is currently using magic (horn is lit).
      * @return

src/main/java/com/minelittlepony/pony/IPonyData.java

@@ -38,6 +38,11 @@ public interface IPonyData {
      */
     int getGlowColor();
 
+    /**
+     * Returns true if and only if this metadata represents a pony that has a horn.
+     */
+    boolean hasHorn();
+
     /**
      * Returns true if and only if this metadata represents a pony that can cast magic.
      */