Fix null object reference

Bug: 281487373
Test: atest android.net.wifi.sharedconnectivity.cts
Change-Id: Iedbf8e041891b7d3aabf8378460a3f1ec4e487a6

wifi/java/src/android/net/wifi/sharedconnectivity/app/SharedConnectivitySettingsState.java

@@ -196,7 +196,7 @@ public final class SharedConnectivitySettingsState implements Parcelable {
     public String toString() {
         return new StringBuilder("SharedConnectivitySettingsState[")
                 .append("instantTetherEnabled=").append(mInstantTetherEnabled)
-                .append("PendingIntent=").append(mInstantTetherSettingsPendingIntent.toString())
+                .append("PendingIntent=").append(mInstantTetherSettingsPendingIntent)
                 .append("extras=").append(mExtras.toString())
                 .append("]").toString();
     }