Mask selection on topology causes memory leak

[tonyyzy]

top = traj.top
while True:
    top[":1"]

This would lead to crashes by using up all system memory.

On pytraj 2.0.6

[tonyyzy]

Note that top.atom(0) leaks memory as well

[hainm]

Thanks @tonyyzy for your reports. It's been a while seeing you.

[hainm]

@tonyyzy I think @hichiaty fixed the issue in master branch in #1617

Cheers

[tonyyzy]

Thanks both! @hainm @hichiaty