gui: picture-in-picture mode may cause segfault on wayland environment

[coveralls]

Pull Request Test Coverage Report for Build 7946529143

Details

• -46 of 68 (32.35%) changed or added relevant lines in 5 files are covered.
• 1 unchanged line in 1 file lost coverage.
• Overall coverage decreased (-0.05%) to 55.429%

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Changes Missing Coverage	Covered Lines	Changed/Added Lines	%
feeluown/player/mpvplayer.py	0	1	0.0%
feeluown/gui/widgets/mpv_.py	7	15	46.67%
feeluown/gui/uimain/nowplaying_overlay.py	6	18	33.33%
feeluown/gui/watch.py	7	32	21.88%
<!--	Total:	22	68	32.35%	-->

Files with Coverage Reduction	New Missed Lines	%
feeluown/gui/uimain/nowplaying_overlay.py	1	67.59%
<!--	Total:	1		-->

Totals
Change from base Build 7927858520:	-0.05%
Covered Lines:	9066
Relevant Lines:	16356

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💛 - Coveralls

[cosven]

@cosven 这个方案并不行 ~