Account for abstract methods in createFieldAccessInfoCollectionModifier()

Change-Id: Idec22d6d6a1c63b5fb8d1cb89a8e099d7f501301
diff --git a/src/main/java/com/android/tools/r8/horizontalclassmerging/HorizontalClassMerger.java b/src/main/java/com/android/tools/r8/horizontalclassmerging/HorizontalClassMerger.java
index fd9fa86..495be54 100644
--- a/src/main/java/com/android/tools/r8/horizontalclassmerging/HorizontalClassMerger.java
+++ b/src/main/java/com/android/tools/r8/horizontalclassmerging/HorizontalClassMerger.java
@@ -121,7 +121,7 @@
           definition -> definition.getCode().isHorizontalClassMergingCode(),
           method -> builder.recordFieldWrittenInContext(group.getClassIdField(), method));
       target.forEachProgramVirtualMethodMatching(
-          definition -> definition.getCode().isHorizontalClassMergingCode(),
+          definition -> definition.hasCode() && definition.getCode().isHorizontalClassMergingCode(),
           method -> builder.recordFieldReadInContext(group.getClassIdField(), method));
     }
     return builder.build();