Add protection against attempting to Unload() multiple times

include/Font.hpp

@@ -101,7 +101,11 @@ class Font : public ::Font {
     }
 
     void Unload() {
-        UnloadFont(*this);
+        // Protect against calling UnloadFont() twice.
+        if (baseSize != 0) {
+            UnloadFont(*this);
+            baseSize = 0;
+        }
     }
 
     GETTERSETTER(int, BaseSize, baseSize)

include/Sound.hpp

@@ -95,7 +95,11 @@ class Sound : public ::Sound {
      * Unload sound
      */
     inline void Unload() {
-        ::UnloadSound(*this);
+        // Protect against calling UnloadSound() twice.
+        if (frameCount != 0) {
+            ::UnloadSound(*this);
+            frameCount = 0;
+        }
     }
 
     /**

include/TextureUnmanaged.hpp

@@ -132,7 +132,11 @@ class TextureUnmanaged : public ::Texture {
      * Unload texture from GPU memory (VRAM)
      */
     inline void Unload() {
-        ::UnloadTexture(*this);
+        // Protect against calling UnloadTexture() twice.
+        if (id != 0) {
+            ::UnloadTexture(*this);
+            id = 0;
+        }
     }
 
     /**

include/Wave.hpp

@@ -161,6 +161,7 @@ class Wave : public ::Wave {
      * Unload wave data
      */
     void Unload() {
+        // Protect against calling UnloadWave() twice.
         if (data != nullptr) {
             ::UnloadWave(*this);
             data = nullptr;