Abort when PTT search table has zero entries

The static analyzer from LLVM/Clang 1:3.4~svn194079-1 reports a possible
allocation of size 0 in `libdvdread/src/ifo_read.c`.

        $ scan-build -o scan-build make
        $ scan-view scan-build/2013-11-18-155601-16168-1

When `vts_ptt_srpt->nr_of_srpts` is zero the allocation size is zero.

        vts_ptt_srpt->title = malloc(vts_ptt_srpt->nr_of_srpts * sizeof(ttu_t));

The manual of the function `malloc` writes the following.

        If size is 0, then malloc() returns either NULL, or a unique
        pointer value that can later be successfully passed to free().

So check for 0 and, if it is, abort by going to the label `fail`.

Patch by Paul Menzel <paulepanter AT users DOT sourceforge DOT net>


git-svn-id: svn://svn.mplayerhq.hu/dvdnav/trunk/libdvdread/src@1289 625a9de0-492d-0410-920c-a7e632af1907
Use 0 instead of NULL in integer comparison

Both GCC 4.8.2 and Clang 3.4 warn about a format mismatch in a
comparison.

        libtool: compile:  gcc -DHAVE_CONFIG_H -I. -I.. -I.. -I../src -mno-ms-bitfields -O3 -Wall -D_FILE_OFFSET_BITS=64 -D_LARGEFILE64_SOUR
CE -MT ifo_read.lo -MD -MP -MF .deps/ifo_read.Tpo -c ifo_read.c  -fPIC -DPIC -o .libs/ifo_read.o
        […]
        ifo_read.c: In function 'ifoRead_PTL_MAIT':
        ifo_read.c:1313:34: warning: comparison between pointer and integer [enabled by default]
           if(ifofile->vmgi_mat->ptl_mait == NULL)

        libtool: compile:  clang -DHAVE_CONFIG_H -I. -I.. -I.. -I../src -O3 -Wall -D_FILE_OFFSET_BITS=64 -D_LARGEFILE64_SOURCE -MT ifo_read.
lo -MD -MP -MF .deps/ifo_read.Tpo -c ifo_read.c  -fPIC -DPIC -o .libs/ifo_read.o
        […]
        ifo_read.c:1313:34: warning: comparison between pointer and integer ('uint32_t' (aka 'unsigned int') and 'void *')
          if(ifofile->vmgi_mat->ptl_mait == NULL)
             ~~~~~~~~~~~~~~~~~~~~~~~~~~~ ^  ~~~~

Fix this by using the integer 0 instead of `NULL`.

Patch by Paul Menzel <paulepanter AT users DOT sourceforge DOT net>



git-svn-id: svn://svn.mplayerhq.hu/dvdnav/trunk/libdvdread/src@1290 625a9de0-492d-0410-920c-a7e632af1907
added gitignore from git svn show-ignore