Avoid external variable whiteTexture

To get it, use GetDefaultTexture()

src/models.c

@@ -50,7 +50,7 @@
 //----------------------------------------------------------------------------------
 // Global Variables Definition
 //----------------------------------------------------------------------------------
-extern unsigned int whiteTexture;
+// ...
 
 //----------------------------------------------------------------------------------
 // Module specific Functions Declaration
@@ -811,7 +811,7 @@ void UnloadMaterial(Material material)
 // Link a texture to a model
 void SetModelTexture(Model *model, Texture2D texture)
 {
-    if (texture.id <= 0) model->material.texDiffuse.id = whiteTexture;  // Use default white texture
+    if (texture.id <= 0) model->material.texDiffuse = GetDefaultTexture();  // Use default white texture
     else model->material.texDiffuse = texture;
 }
 

src/rlgl.c

@@ -228,8 +228,7 @@ static PFNGLDELETEVERTEXARRAYSOESPROC glDeleteVertexArrays;
 static int blendMode = 0;
 
 // White texture useful for plain color polys (required by shader)
-// NOTE: It's required in shapes and models modules!
-unsigned int whiteTexture;
+static unsigned int whiteTexture;
 
 //----------------------------------------------------------------------------------
 // Module specific Functions Declaration

src/shapes.c

@@ -44,7 +44,7 @@
 //----------------------------------------------------------------------------------
 // Global Variables Definition
 //----------------------------------------------------------------------------------
-extern unsigned int whiteTexture;
+// ...
 
 //----------------------------------------------------------------------------------
 // Module specific Functions Declaration
@@ -137,7 +137,7 @@ void DrawCircleV(Vector2 center, float radius, Color color)
     }
     else if ((rlGetVersion() == OPENGL_33) || (rlGetVersion() == OPENGL_ES_20))
     {
-        rlEnableTexture(whiteTexture); // Default white texture
+        rlEnableTexture(GetDefaultTexture().id); // Default white texture
 
         rlBegin(RL_QUADS);
             for (int i = 0; i < 360; i += 20)
@@ -220,7 +220,7 @@ void DrawRectangleV(Vector2 position, Vector2 size, Color color)
     }
     else if ((rlGetVersion() == OPENGL_33) || (rlGetVersion() == OPENGL_ES_20))
     {
-        rlEnableTexture(whiteTexture); // Default white texture
+        rlEnableTexture(GetDefaultTexture().id); // Default white texture
 
         rlBegin(RL_QUADS);
             rlColor4ub(color.r, color.g, color.b, color.a);