Account for null value in StatefulObjectValue.equals

Bug: 216096564
Change-Id: Ifc5deeea4444ee7621628534319b3ee8695f822f

src/main/java/com/android/tools/r8/ir/analysis/value/StatefulObjectValue.java

diff --git a/src/main/java/com/android/tools/r8/ir/analysis/value/StatefulObjectValue.java b/src/main/java/com/android/tools/r8/ir/analysis/value/StatefulObjectValue.java
index 39174da..5459666 100644
--- a/src/main/java/com/android/tools/r8/ir/analysis/value/StatefulObjectValue.java
+++ b/src/main/java/com/android/tools/r8/ir/analysis/value/StatefulObjectValue.java
@@ -71,7 +71,10 @@
 
   @Override
   public boolean equals(Object o) {
-    if (getClass() != o.getClass()) {
+    if (o == this) {
+      return true;
+    }
+    if (o == null || getClass() != o.getClass()) {
       return false;
     }
     StatefulObjectValue statefulObjectValue = (StatefulObjectValue) o;