Add double quotes around argument to exec

To handle directories with spaces.

Author: dave-finlay

bin/promtimer

@@ -1,4 +1,5 @@
 #!/bin/sh
 
-export PROMTIMER_DIR="$(dirname "$0")/.."
-exec $PROMTIMER_DIR/promtimer/promtimer.py $@
+PROMTIMER_DIR="$(dirname "$0")/.."
+export PROMTIMER_DIR
+exec "$PROMTIMER_DIR/promtimer/promtimer.py" $@