Fix the GB_run_frame API in SGB mode

Core/gb.c

@@ -351,6 +351,8 @@ exit:
 
 uint8_t GB_run(GB_gameboy_t *gb)
 {
+    gb->vblank_just_occured = false;
+
     if (gb->sgb && gb->sgb->intro_animation < 140) {
         /* On the SGB, the GB is halted after finishing the boot ROM.
            Then, after the boot animation is almost done, it's reset.

Core/z80_cpu.c

@@ -1356,8 +1356,6 @@ static GB_opcode_t *opcodes[256] = {
 };
 void GB_cpu_run(GB_gameboy_t *gb)
 {
-    gb->vblank_just_occured = false;
-
     if (gb->hdma_on) {
         GB_advance_cycles(gb, 4);
         return;