Fix memory leak in broken file in JBIG2Stream::readGenericBitmap

It could happen that codingLine succeeds but refLine fails because we're
just on the edge of the allocatable memory so free codingLine just in
case
7 jobs for fix_potential_leak in 6 minutes and 8 seconds (queued for 3 seconds)
Status Job ID Name Coverage
  Build
passed #7462958
build

00:03:36

passed #7462963
build_android

00:00:47

passed #7462959
build_clang_libcpp

00:06:08

passed #7462962
build_clazy

00:05:02

passed #7462961
build_mingw64_fedora

00:02:35

passed #7462960
build_ubuntu_16_04

00:01:58

passed #7462957
clang_format

00:01:40