Improve SETextBox word selection

Fix explicit null dereference CID 18129
Fix dereference after null check CID 18130
Fix dereference after null check CID 18133
Fix dereference after null check CID 18143
Fix exception resource leak CID 18146
Fix dereference after null check CID 18147
Fix null return value dereference CID 18162
Fix explicit null dereference CID 18173
Fix dereference after null check CID 18181
Fix dereference after null check CID 18183
Fix dereference after null check CID 18191
Fix dereference after null check CID 18197
Fix dereference after null check CID 83028
Fix dereference after null check CID 83007
Fix exception resource leak CID 60869
Matroska + TS progress speed up
Deduplicate progress methods
nl-NL translation: minor corrections/improvements + new tags
nl-NL translation: spcorr + experiment (buttons)
nl-NL translation: preferences 1