Avoid a crash in FcPatternHash with ranges

When a cached pattern contains a range,
FcPatternHash will crash.

Fixes #254.
10 jobs for pattern-hash-crash in 5 minutes and 43 seconds (queued for 2 seconds)
Status Job ID Name Coverage
  Build
passed #4233029
gst-macos-10.15
meson macos

00:00:49

passed #4233026
meson-mingw-w64-build

00:03:51

manual #4233030
docker windows 1809 allowed to fail manual
meson msys2
passed #4233024
meson-shared-build

00:03:38

passed #4233025
meson-static-build

00:04:28

passed #4233027
docker windows 1809
meson vs2017 amd64

00:01:07

passed #4233028
docker windows 1809
meson vs2017 x86

00:01:08

passed #4233023
mingw-build

00:04:45

passed #4233021
shared-build

00:05:43

passed #4233022
static-build

00:04:44