Fix #597: Pop namespace scope after NsReader::read_to_end

[Mingun]

I want to check that the changes does not break anything else when read_to_end would be called after each possible returned events, but now I'm too lazy to finish the tests. Will do that on weekend.

[codecov-commenter]

Codecov Report

Merging #598 (a619fc1) into master (9fb797e) will increase coverage by 0.08%. The diff coverage is 100.00%.

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@@            Coverage Diff             @@
##           master     #598      +/-   ##
==========================================
+ Coverage   64.38%   64.47%   +0.08%     
==========================================
  Files          35       35              
  Lines       16676    16676              
==========================================
+ Hits        10737    10752      +15     
+ Misses       5939     5924      -15     

Flag	Coverage Δ
unittests	64.47% <100.00%> (+0.08%)	:arrow_up:

Flags with carried forward coverage won't be shown. Click here to find out more.

Impacted Files	Coverage Δ
src/reader/ns_reader.rs	68.14% <100.00%> (+4.42%)	:arrow_up:

... and 4 files with indirect coverage changes