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

Source/Core/VideoBackends/OGL/ProgramShaderCache.cpp

@@ -494,6 +494,12 @@ void ProgramShaderCache::InvalidateVertexFormat()
   s_last_VAO = 0;
 }
 
+void ProgramShaderCache::InvalidateVertexFormatIfBound(GLuint vao)
+{
+  if (s_last_VAO == vao)
+    s_last_VAO = 0;
+}
+
 void ProgramShaderCache::InvalidateLastProgram()
 {
   CurrentProgram = 0;

Source/Core/VideoBackends/OGL/ProgramShaderCache.h

@@ -72,6 +72,7 @@ class ProgramShaderCache
   static void BindVertexFormat(const GLVertexFormat* vertex_format);
   static bool IsValidVertexFormatBound();
   static void InvalidateVertexFormat();
+  static void InvalidateVertexFormatIfBound(GLuint vao);
   static void InvalidateLastProgram();
 
   static bool CompileComputeShader(SHADER& shader, const std::string& code);