Adds ERROR state to ImsConfig

Adds the ERROR return state for bool provisioning values
so that we can throw an Exception in some cases.

Bug: 64540800
Test: Manual
Change-Id: I0b79837c694d245999031ec65783857e114b7c75
diff --git a/telephony/java/com/android/ims/ImsConfig.java b/telephony/java/com/android/ims/ImsConfig.java
index e7b22bd..cf4c47b 100644
--- a/telephony/java/com/android/ims/ImsConfig.java
+++ b/telephony/java/com/android/ims/ImsConfig.java
@@ -524,6 +524,7 @@
     * Defines IMS feature value.
     */
     public static class FeatureValueConstants {
+        public static final int ERROR = -1;
         public static final int OFF = 0;
         public static final int ON = 1;
     }