Segmented small maps can not be converted to .nvm files using model_converter

[Yzhbuaa]

@AIBluefisher, hello, I found that the segmented small maps can not be converted to .nvm files using model_converter. I am sure that I can convert the map in folder 0 or folder partition_0 to partition_x(x denotes the total number of partitions) to .nvm files successfully. Here is is the output of model_converter. Thank you!

terminate called after throwing an instance of 'std::out_of_range'
what(): _Map_base::at
*** Aborted at 1599813927 (unix time) try "date -d @1599813927" if you are using GNU date ***
PC: @ 0x7fe1ad59ef47 gsignal
*** SIGABRT (@0x3e8000054a6) received by PID 21670 (TID 0x7fe1b249d980) from PID 21670; stack trace: ***
@ 0x7fe1b0a808a0 (unknown)
@ 0x7fe1ad59ef47 gsignal
@ 0x7fe1ad5a08b1 abort
@ 0x7fe1adfa087e (unknown)
@ 0x7fe1adfac486 (unknown)
@ 0x7fe1adfac4f1 std::terminate()
@ 0x7fe1adfac745 __cxa_throw
@ 0x7fe1adfa300e std::__throw_out_of_range()
@ 0x55828280efe7 (unknown)
@ 0x55828275219d (unknown)
@ 0x558282744bc8 (unknown)
@ 0x7fe1ad581b97 __libc_start_main
@ 0x55828274ef4a (unknown)
[1] 21670 abort (core dumped)

I notice that all the segmented small maps have the same number of cameras(in my case, 461).