check if quickfix buffer is empty

[Konfekt]

In

quickfix-reflector.vim/plugin/quickfix-reflector.vim

Line 37 in 6a6a9e2

execute 'write! quickfix-' . bufnr('%')

there could be a check if quickfix-' . bufnr('%') is empty before writing to avoid

Error detected while processing function <SNR>247_parse_flags[84]..<SNR>247_start[16]..<SNR>247_run[3]..BufRead Autocommands for "quickfix"..function <SNR>236_OnQuickfixInit:
line   10:
E749: Empty buffer