TizenRendererEvasGL: Add nullcheck for evas_gl_

[JSUYA]

DestorySurface is called more than once depending on the situation.
Add nullcheck to avoid destroying already destroyed evas_gl_ again.

related issue : #319

[swift-kim]

How about setting evas_gl_ to nullptr and checking it before performing the destruction?

[swift-kim]

~TizenRendererEgl failed after applying this patch. Can be reproduced in the same way as #319.

* thread #1, name = 'Runner.dll', stop reason = signal SIGABRT
  * frame #0: 0xb779ea49 [vdso]`__kernel_vsyscall + 9
    frame #1: 0xb72ad166 libc.so.6`__GI_raise + 214
    frame #2: 0xb72943ce libc.so.6`__GI_abort + 281
    frame #3: 0xb729429e libc.so.6`__assert_fail_base.cold + 17
    frame #4: 0xb72a4d06 libc.so.6`__GI___assert_fail + 86
    frame #5: 0xa82f0f47 libtpl-egl.so.1`___lldb_unnamed_symbol39$$libtpl-egl.so.1 + 1735
    frame #6: 0xa82eb692 libtpl-egl.so.1`___lldb_unnamed_symbol7$$libtpl-egl.so.1 + 146
    frame #7: 0xa82eb32e libtpl-egl.so.1`tpl_object_unreference + 94
    frame #8: 0xa834ac6d libEGL.so`___lldb_unnamed_symbol245$$libEGL.so + 109
    frame #9: 0xa834a28f libEGL.so`___lldb_unnamed_symbol210$$libEGL.so + 47
    frame #10: 0xa8348538 libEGL.so`___lldb_unnamed_symbol175$$libEGL.so + 72
    frame #11: 0xa8349251 libEGL.so`yagl_resource_release + 33
    frame #12: 0xa834a381 libEGL.so`___lldb_unnamed_symbol213$$libEGL.so + 33
    frame #13: 0xa833f6c6 libEGL.so`eglDestroySurface + 230
    frame #14: 0xa7794144 libflutter_tizen.so`flutter::TizenRendererEgl::DestroySurface() + 68
    frame #15: 0xa779376a libflutter_tizen.so`flutter::TizenRendererEgl::~TizenRendererEgl() + 42
    frame #16: 0xa7786d73 libflutter_tizen.so`flutter::FlutterTizenEngine::~FlutterTizenEngine() + 99
    frame #17: 0xa77870f2 libflutter_tizen.so`flutter::FlutterTizenEngine::~FlutterTizenEngine() + 34
    frame #18: 0xa778aa65 libflutter_tizen.so`flutter::FlutterTizenView::~FlutterTizenView() + 181
    frame #19: 0xa778aa92 libflutter_tizen.so`flutter::FlutterTizenView::~FlutterTizenView() + 34
    frame #20: 0xa7786695 libflutter_tizen.so`FlutterDesktopViewDestroy + 37

[JSUYA]

How about setting evas_gl_ to nullptr and checking it before performing the destruction?

I considered your idea first. However, I thought that renderer's Destroy being called twice was a problem in itself. I think it's a side effect of #304.

[JSUYA]

~TizenRendererEgl failed after applying this patch. Can be reproduced in the same way as #319.

oh i will check

[JSUYA]

How about setting evas_gl_ to nullptr and checking it before performing the destruction?

I considered your idea first. However, I thought that renderer's Destroy being called twice was a problem in itself. I think it's a side effect of #304.

I added null check as per your comment.
StopEngine is called twice. I will discussed again when @bbrto21 returns to the office.