fix recent issue combining -r with empty list of input files

This would resize the table of input filenames to zero,
delivering an empty table,
to which it was no longer possible to add stdin.

tests/playTests.sh

@@ -142,7 +142,7 @@ ZSTD_CLEVEL=-   $ZSTD -f tmp # malformed env var, warn and revert to default set
 ZSTD_CLEVEL=a   $ZSTD -f tmp # malformed env var, warn and revert to default setting
 ZSTD_CLEVEL=+a  $ZSTD -f tmp # malformed env var, warn and revert to default setting
 ZSTD_CLEVEL=3a7 $ZSTD -f tmp # malformed env var, warn and revert to default setting
-ZSTD_CLEVEL=50000000000  $ZSTD -f tmp # numeric value too large, warn and revert to default setting
+ZSTD_CLEVEL=50000000000 $ZSTD -f tmp # numeric value too large, warn and revert to default setting
 println "test : override ZSTD_CLEVEL with command line option"
 ZSTD_CLEVEL=12  $ZSTD --fast=3 -f tmp # overridden by command line option
 println "test : compress to stdout"
@@ -239,18 +239,24 @@ if [[ $file2timestamp -ge $file1timestamp ]]; then
 else
   println "Test is not successful"
 fi
-#File Extension check.
+# File Extension check.
 ./datagen $size > precompressedFilterTestDir/input.zstbar
 $ZSTD --exclude-compressed --long --rm -r precompressedFilterTestDir
-#ZSTD should compress input.zstbar
+# ZSTD should compress input.zstbar
 test -f precompressedFilterTestDir/input.zstbar.zst
-#Check without the --exclude-compressed flag
+# Check without the --exclude-compressed flag
 $ZSTD --long --rm -r precompressedFilterTestDir
-#Files should get compressed again without the --exclude-compressed flag.
+# Files should get compressed again without the --exclude-compressed flag.
 test -f precompressedFilterTestDir/input.5.zst.zst
 test -f precompressedFilterTestDir/input.6.zst.zst
 println "Test completed"
 
+
+println "\n===>  recursive mode test "
+# combination of -r with empty list of input file
+$ZSTD -c -r < tmp > tmp.zst
+
+
 println "\n===>  file removal"
 $ZSTD -f --rm tmp
 test ! -f tmp  # tmp should no longer be present