CUR_TIME=`echo $SQLQTIME$MARK$SQLQGRMARK | $MYSQL`
OLD_TIME=`echo $SQLQTIME$LASTMARK$SQLQGRMARK | $MYSQL`
-((DELTA=$CUR_CENTS-$OLD_CENTS))
+if [ -z "$CUR_TIME" -o -z "$OLD_TIME"]; then
+ cat <<EOT
+
+ Unable to calculate total time amounts:
+
+ $SQLQTIME$MARK$SQLQGRMARK
+
+ or
+
+ $SQLQTIME$LASTMARK$SQLQGRMARK
+
+ gave an empty result
+
+EOT
+fi
+
+((DELTA=$CUR_TIME-$OLD_TIME))
if [ $DELTA -lt 0 ]; then
PERC=0
else