Crash in add_ch_to_localbuffer

[lluchs]

vzlogger randomly crashed today:

#0  0x0053c2cc in Reading::deleted (this=0xb)
    at /home/lukas/.cache/yay/vzlogger-git/src/vzlogger/include/Reading.hpp:173
#1  0x0053b648 in add_ch_to_localbuffer (ch=...)
    at /home/lukas/.cache/yay/vzlogger-git/src/vzlogger/src/local.cpp:87
#2  0x005431ac in reading_thread (arg=0x15b3c80)
    at /home/lukas/.cache/yay/vzlogger-git/src/vzlogger/src/threads.cpp:140
#3  0xb6ee9f60 in start_thread () from /usr/lib/libpthread.so.0
#4  0xb6912cd8 in ?? () from /usr/lib/libc.so.6

The log showed connection errors shortly before the crash (at 06:12:11):

361050 [Dec 09 06:11:41][chn0] CURL: Couldn't connect to server                        
361051 [Dec 09 06:11:41][chn0] Waiting 30 secs for next request due to previous failure
361052 [Dec 09 06:11:41][chn1] CURL: Couldn't connect to server                        
361053 [Dec 09 06:11:41][chn1] Waiting 30 secs for next request due to previous failure

System is Arch Linux ARM (armv7l), vzlogger commit 037ab6b (current master).

[r00t-]

	for (it = buf->begin(); it != buf->end(); ++it) {
		Reading &r = *it;
		if (!r.deleted()) {

https://github.com/volkszaehler/vzlogger/blob/master/src/local.cpp#L87
(the method then crashes dereferencing this->_deleted.)

i can't tell if it's expected that buf contains a null-entry,
but it would be trivial to add a check.

thanks for reporting, @lluchs!