Do not fail cogsetup.sh if repo is not in PATH

Change-Id: Id1588ac710963d14edfb485daf2b3b14c857ae69
diff --git a/cogsetup.sh b/cogsetup.sh
index 44538f2..ef1485d 100644
--- a/cogsetup.sh
+++ b/cogsetup.sh
@@ -52,7 +52,9 @@
   # it with this function. If the user is running repo within a Cog workspace,
   # we'll fail with an error, otherwise, we run the original repo command with
   # the given args.
-  ORIG_REPO_PATH=`which repo`
+  if ! ORIG_REPO_PATH=`which repo`; then
+    return 0
+  fi
   function repo {
     if [[ "${PWD}" == /google/cog/* ]]; then
       echo "\e[01;31mERROR:\e[0mrepo command is disallowed within Cog workspaces."