cmd/bent: fix cpuprofile command

Change-Id: Ia20ad3e7daa4741a9a3f8675c782f647595f2c5e
Reviewed-on: https://go-review.googlesource.com/c/benchmarks/+/614775
Reviewed-by: Michael Knyszek <mknyszek@google.com>
LUCI-TryBot-Result: Go LUCI <golang-scoped@luci-project-accounts.iam.gserviceaccount.com>
diff --git a/cmd/bent/scripts/cpuprofile b/cmd/bent/scripts/cpuprofile
index e16ce41..93cce07 100755
--- a/cmd/bent/scripts/cpuprofile
+++ b/cmd/bent/scripts/cpuprofile
@@ -1,6 +1,6 @@
 #!/bin/bash
 # Run args as command, but run cpuprofile and then pprof to capture test cpuprofile output
-if [ -n ${BENT_PGO} ] ; then
+if [ -n "${BENT_PGO}" ] ; then
     pf="${BENT_PGO}/${BENT_BENCH}.prof"
     mkdir -p ${BENT_PGO}
 else