Correcting error in bb_asl_proc --> The script fails if there are no json files

bb_asl_pipeline/bb_asl_proc

@@ -40,8 +40,10 @@ if [ ! -z $src/ASL/BASIL/ ]; then
     fi
 fi
 
-for fil in $src/ASL/raw/*.json ; do 
-    bb_read_json_field.py -F $fil -f PhaseEncodingDirection; 
+for fil in $src/ASL/raw/*.json ; do
+    if [ -f $fil ] ; then
+        bb_read_json_field.py -F $fil -f PhaseEncodingDirection;
+    fi
 done > $src/ASL/BASIL/grot.txt
 
 t=`cat $src/ASL/BASIL//grot.txt | grep i | wc -l`