Bug#846499: qstopmotion: FTBFS: tries to compare va_list to NULL

[Aaron M. Ucko]

Source: qstopmotion
Version: 2.3.2-1
Severity: important
Justification: fails to build from source

Builds of qstopmotion on platforms (arm64 so far) on which va_list
isn't simply a pointer have been failing:

  /«PKGBUILDDIR»/src/technical/grabber/gphoto2/gpgrabber.cpp: In static member function 'static void GphotoGrabber::errorDumper(GPLogLevel, const char*, const char*, va_list, void*)':
  /«PKGBUILDDIR»/src/technical/grabber/gphoto2/gpgrabber.cpp:814:17: warning: NULL used in arithmetic [-Wpointer-arith]
       if (args != NULL) {
                   ^~~~
  /«PKGBUILDDIR»/src/technical/grabber/gphoto2/gpgrabber.cpp:814:14: error: invalid operands of types 'va_list {aka __va_list}' and 'long int' to binary 'operator!='
       if (args != NULL) {
                ^
  CMakeFiles/qstopmotion.dir/build.make:1817: recipe for target 'CMakeFiles/qstopmotion.dir/src/technical/grabber/gphoto2/gpgrabber.cpp.o' failed

In general, it's best practice to treat va_list as an opaque type and
avoid making any assumptions about its form.

Could you please take a look?

Thanks!

-- 
Aaron M. Ucko, KB1CJC (amu at alum.mit.edu, ucko at debian.org)
http://www.mit.edu/~amu/ | http://stuff.mit.edu/cgi/finger/?amu@monk.mit.edu