Set the hiddenApiRestrictionOffset in the new DexBackedDexFile constructor

This fixes the build. That's what I get for rebasing changes and not
testing.
diff --git a/dexlib2/src/main/java/org/jf/dexlib2/dexbacked/DexBackedDexFile.java b/dexlib2/src/main/java/org/jf/dexlib2/dexbacked/DexBackedDexFile.java
index 95b7d94..4bede40 100644
--- a/dexlib2/src/main/java/org/jf/dexlib2/dexbacked/DexBackedDexFile.java
+++ b/dexlib2/src/main/java/org/jf/dexlib2/dexbacked/DexBackedDexFile.java
@@ -99,6 +99,13 @@
         classCount = dexBuffer.readSmallUint(HeaderItem.CLASS_COUNT_OFFSET);
         classStartOffset = dexBuffer.readSmallUint(HeaderItem.CLASS_START_OFFSET);
         mapOffset = dexBuffer.readSmallUint(HeaderItem.MAP_OFFSET);
+
+        MapItem mapItem = getMapItemForSection(ItemType.HIDDENAPI_CLASS_DATA_ITEM);
+        if (mapItem != null) {
+            hiddenApiRestrictionsOffset = mapItem.getOffset();
+        } else {
+            hiddenApiRestrictionsOffset = NO_OFFSET;
+        }
     }
 
     protected DexBackedDexFile(@Nullable Opcodes opcodes, @Nonnull DexBuffer dexBuffer, @Nonnull DexBuffer dataBuffer, int offset, boolean verifyMagic) {