[][mt76-vendor: fix more coverity errors]

[Description]
Fix some more coverity errors related to NULL check for mt76-vendor.

[Release-log]
N/A

Change-Id: I096dd26bb6662d4f3e495707231f9ba482e0cc9a
Reviewed-on: https://gerrit.mediatek.inc/c/openwrt/feeds/mtk_openwrt_feeds/+/5072762
diff --git a/feed/mt76-vendor/src/capi.c b/feed/mt76-vendor/src/capi.c
index efdd1d0..f6e683b 100644
--- a/feed/mt76-vendor/src/capi.c
+++ b/feed/mt76-vendor/src/capi.c
@@ -57,6 +57,8 @@
 		return false;
 
 	data = nla_nest_start(msg, NL80211_ATTR_VENDOR_DATA | NLA_F_NESTED);
+	if (!data)
+		return -ENOMEM;
 
 	mt76_ap_rfeatures_set_attr(msg, argc, argv);
 
@@ -125,6 +127,8 @@
 		return false;
 
 	data = nla_nest_start(msg, NL80211_ATTR_VENDOR_DATA | NLA_F_NESTED);
+	if (!data)
+		return -ENOMEM;
 
 	mt76_ap_wireless_set_attr(msg, argc, argv);