Add doc to getNetworkCapabilities

Test: doc-only change
Fixes: 158092418
Change-Id: Ic20fb55e1bdd4e836468794d1f86d3e9d0bc5965
diff --git a/framework/src/android/net/ConnectivityManager.java b/framework/src/android/net/ConnectivityManager.java
index 4636abb..e0b9229 100644
--- a/framework/src/android/net/ConnectivityManager.java
+++ b/framework/src/android/net/ConnectivityManager.java
@@ -1561,7 +1561,7 @@
 
     /**
      * Get the {@link NetworkCapabilities} for the given {@link Network}.  This
-     * will return {@code null} if the network is unknown.
+     * will return {@code null} if the network is unknown or if the |network| argument is null.
      *
      * This will remove any location sensitive data in {@link TransportInfo} embedded in
      * {@link NetworkCapabilities#getTransportInfo()}. Some transport info instances like