Corrected issue, flag not supported...

...by emscripten glfw javascript implementation

src/core.c

@@ -1901,8 +1901,10 @@ static bool InitGraphicsDevice(int width, int height)
     if (configFlags & FLAG_WINDOW_UNDECORATED) glfwWindowHint(GLFW_DECORATED, GL_FALSE);    // Border and buttons on Window
     else glfwWindowHint(GLFW_DECORATED, GL_TRUE);   // Decorated window
     
+#if !defined(PLATFORM_WEB)  // FLAG_WINDOW_TRANSPARENT not supported on HTML5
     if (configFlags & FLAG_WINDOW_TRANSPARENT) glfwWindowHint(GLFW_TRANSPARENT_FRAMEBUFFER, GLFW_TRUE);     // Transparent framebuffer
     else glfwWindowHint(GLFW_TRANSPARENT_FRAMEBUFFER, GLFW_FALSE);  // Opaque framebuffer
+#endif
 
     if (configFlags & FLAG_MSAA_4X_HINT) glfwWindowHint(GLFW_SAMPLES, 4);   // Tries to enable multisampling x4 (MSAA), default is 0