meta: Fix saving the active program

When saving the active program in _mesa_meta_begin, it was actually
saving the fragment program instead. This means that if the
application binds a program that only has a vertex shader then when
the meta saved state is restored it will forget the bound program.

Bugzilla: https://bugs.freedesktop.org/show_bug.cgi?id=41969
Reviewed-by: Chad Versace <chad@chad-versace.us>

src/mesa/drivers/common/meta.c

@@ -464,7 +464,7 @@ _mesa_meta_begin(struct gl_context *ctx, GLbitfield state)
 	 _mesa_reference_shader_program(ctx, &save->FragmentShader,
 					ctx->Shader.CurrentFragmentProgram);
 	 _mesa_reference_shader_program(ctx, &save->ActiveShader,
-					ctx->Shader.CurrentFragmentProgram);
+					ctx->Shader.ActiveProgram);
 
          _mesa_UseProgramObjectARB(0);
       }