check not null before accessing by index (#2243)

src/rmodels.c

@@ -1624,7 +1624,7 @@ void UnloadMesh(Mesh mesh)
     // Unload rlgl mesh vboId data
     rlUnloadVertexArray(mesh.vaoId);
 
-    for (int i = 0; i < MAX_MESH_VERTEX_BUFFERS; i++) rlUnloadVertexBuffer(mesh.vboId[i]);
+    if (mesh.vboId != NULL) for (int i = 0; i < MAX_MESH_VERTEX_BUFFERS; i++) rlUnloadVertexBuffer(mesh.vboId[i]);
     RL_FREE(mesh.vboId);
 
     RL_FREE(mesh.vertices);
@@ -1787,9 +1787,12 @@ void UnloadMaterial(Material material)
     if (material.shader.id != rlGetShaderIdDefault()) UnloadShader(material.shader);
 
     // Unload loaded texture maps (avoid unloading default texture, managed by raylib)
-    for (int i = 0; i < MAX_MATERIAL_MAPS; i++)
+    if (material.maps != NULL)
     {
-        if (material.maps[i].texture.id != rlGetTextureIdDefault()) rlUnloadTexture(material.maps[i].texture.id);
+        for (int i = 0; i < MAX_MATERIAL_MAPS; i++)
+        {
+            if (material.maps[i].texture.id != rlGetTextureIdDefault()) rlUnloadTexture(material.maps[i].texture.id);
+        }
     }
 
     RL_FREE(material.maps);