tests/fate-run: Sanitize test argument

test -z is a binary operator.

Signed-off-by: Andreas Rheinhardt <andreas.rheinhardt@outlook.com>

tests/fate-run.sh

@@ -243,7 +243,7 @@ enc_dec(){
         -f $dec_fmt_out -y $tdecfile || return
     do_md5sum $decfile
     tests/tiny_psnr${HOSTEXECSUF} $srcfile $decfile $cmp_unit $cmp_shift
-    test -z $ffprobe_opts || \
+    test -z "$ffprobe_opts" || \
         run ffprobe${PROGSUF}${EXECSUF} -bitexact $ffprobe_opts $tencfile || return
 }
 
@@ -268,7 +268,7 @@ transcode(){
     echo $(wc -c $encfile)
     ffmpeg $DEC_OPTS $final_decode -i $tencfile $ENC_OPTS $FLAGS $final_encode \
         -f framecrc - || return
-    test -z $ffprobe_opts || \
+    test -z "$ffprobe_opts" || \
         run ffprobe${PROGSUF}${EXECSUF} -bitexact $ffprobe_opts $tencfile || return
 }
 
@@ -288,7 +288,7 @@ stream_remux(){
         -f $enc_fmt -y $tencfile || return
     ffmpeg $DEC_OPTS -i $tencfile $ENC_OPTS $FLAGS $final_decode \
         -f framecrc - || return
-    test -z $ffprobe_opts || \
+    test -z "$ffprobe_opts" || \
         run ffprobe${PROGSUF}${EXECSUF} -bitexact $ffprobe_opts $tencfile || return
 }