OGL: Fix binding error on shutdown

This was occurring if the imgui vertex format was bound on shutdown,
which is destroyed before the vertex buffers

Source/Core/VideoBackends/OGL/NativeVertexFormat.cpp

@@ -80,6 +80,7 @@ GLVertexFormat::GLVertexFormat(const PortableVertexDeclaration& vtx_decl)
 
 GLVertexFormat::~GLVertexFormat()
 {
+  ProgramShaderCache::InvalidateVertexFormatIfBound(VAO);
   glDeleteVertexArrays(1, &VAO);
 }
 }  // namespace OGL