fix: update bundle channel

Makefile

@@ -10,6 +10,7 @@ VERSION ?= 0.0.1
 # To re-generate a bundle for other specific channels without changing the standard setup, you can:
 # - use the CHANNELS as arg of the bundle target (e.g make bundle CHANNELS=candidate,fast,stable)
 # - use environment variables to overwrite this value (e.g export CHANNELS="candidate,fast,stable")
+CHANNELS ?= "stable"
 ifneq ($(origin CHANNELS), undefined)
 BUNDLE_CHANNELS := --channels=$(CHANNELS)
 endif
@@ -19,6 +20,7 @@ endif
 # To re-generate a bundle for any other default channel without changing the default setup, you can:
 # - use the DEFAULT_CHANNEL as arg of the bundle target (e.g make bundle DEFAULT_CHANNEL=stable)
 # - use environment variables to overwrite this value (e.g export DEFAULT_CHANNEL="stable")
+DEFAULT_CHANNEL ?= "stable"
 ifneq ($(origin DEFAULT_CHANNEL), undefined)
 BUNDLE_DEFAULT_CHANNEL := --default-channel=$(DEFAULT_CHANNEL)
 endif