audio: fix offload enabling test parameter

passing NULL as the default to property_get doesn't return false,
it returns random memory junk that evaluates to true... Explicitly
default the state of this property to "false" as a default

Change-Id: Ib2808bf2540b2b4fdf754d489fb44aa5d9e061a8
diff --git a/audio/AudioPolicyManagerBase.cpp b/audio/AudioPolicyManagerBase.cpp
index ea37624..fcedd43 100644
--- a/audio/AudioPolicyManagerBase.cpp
+++ b/audio/AudioPolicyManagerBase.cpp
@@ -1491,7 +1491,7 @@
     //TODO: enable audio offloading with video when ready
     if (offloadInfo.has_video)
     {
-        if(property_get("av.offload.enable", propValue, NULL)) {
+        if(property_get("av.offload.enable", propValue, "false")) {
             bool prop_enabled = atoi(propValue) || !strncmp("true", propValue, 4);
             if (!prop_enabled) {
                ALOGW("offload disabled by av.offload.enable = %s ", propValue );