GT-0 fixing junit tests

Ghidra/Features/Base/src/main/java/ghidra/app/util/viewer/util/AddressBasedIndexMapper.java

@@ -37,8 +37,9 @@ public class AddressBasedIndexMapper implements IndexMapper {
 	public BigInteger map(BigInteger value) {
 		Address address = from.getAddress(value);
 		if (address == null) {
-			return null;
+			return BigInteger.ZERO;
 		}
-		return to.getIndex(address);
+		BigInteger mapped = to.getIndex(address);
+		return mapped != null ? mapped : BigInteger.ZERO;
 	}
 }

Ghidra/Framework/Docking/src/main/java/docking/widgets/fieldpanel/listener/IndexMapper.java

@@ -33,5 +33,11 @@ public interface IndexMapper {
 		}
 	};
 
+	/**
+	 * Maps an index from one address mapping to another. This method will return
+	 * {@link BigInteger#ZERO} if there no mapping. 
+	 * @param value the index value to map from an old index map to a new index map
+	 * @return the mapped index
+	 */
 	public BigInteger map(BigInteger value);
 }