FAIL - Ubuntu 16.04.3 - Githubissues

Installation fail on Ubuntu 16.04.3. How to fix?
root@ubuntu-s-1vcpu-1gb-ams2-01:~# apt-get install libopal-dev
root@ubuntu-s-1vcpu-1gb-ams2-01:~/sipcmd# make
g++ -c -Wall  src/main.cpp -o src/main.o -I/usr/include/opal -I/usr/include/ptlib -Isrc/ -g -DDEBUG
In file included from /usr/include/opal/h323/h323.h:39:0,
                 from src/includes.h:25,
                 from src/main.h:24,
                 from src/main.cpp:24:
/usr/include/opal/h323/h323ep.h:148:30: warning: converting to non-pointer type 'unsigned int' from NULL [-Wconversion-null]
       unsigned int options = NULL,      ///<  options to pass to conneciton
                              ^
src/main.cpp: In member function 'bool Manager::SendDTMF(const PString&)':
src/main.cpp:446:18: warning: comparison between signed and unsigned integer expressions [-Wsign-compare]
         for (; i < dtmf.GetSize() - 1; i++) {
                  ^
src/main.cpp:459:17: warning: comparison between signed and unsigned integer expressions [-Wsign-compare]
         ok = (i == dtmf.GetSize() - 1 ? true : false);
                 ^
g++ -c -Wall  src/commands.cpp -o src/commands.o -I/usr/include/opal -I/usr/include/ptlib -Isrc/ -g -DDEBUG
In file included from /usr/include/opal/h323/h323.h:39:0,
                 from src/includes.h:25,
                 from src/main.h:24,
                 from src/state.h:25,
                 from src/commands.cpp:29:
/usr/include/opal/h323/h323ep.h:148:30: warning: converting to non-pointer type 'unsigned int' from NULL [-Wconversion-null]
       unsigned int options = NULL,      ///<  options to pass to conneciton
                              ^
src/commands.cpp: In member function 'virtual bool Wait::ParseCommand(const char**, std::vector<Command*>&)':
src/commands.cpp:439:30: warning: format '%u' expects argument of type 'unsigned int*', but argument 3 has type 'size_t* {aka long unsigned int*}' [-Wformat=]
   sscanf(*cmds, "%u", &millis);
                              ^
g++ -c -Wall  src/channels.cpp -o src/channels.o -I/usr/include/opal -I/usr/include/ptlib -Isrc/ -g -DDEBUG
In file included from /usr/include/opal/h323/h323.h:39:0,
                 from src/includes.h:25,
                 from src/channels.h:25,
                 from src/channels.cpp:27:
/usr/include/opal/h323/h323ep.h:148:30: warning: converting to non-pointer type 'unsigned int' from NULL [-Wconversion-null]
       unsigned int options = NULL,      ///<  options to pass to conneciton
                              ^
g++ src/main.o src/commands.o src/channels.o -o sipcmd -lopal -lpt
tmakkonen / sipcmd

FAIL - Ubuntu 16.04.3 #56
