add consumer code to account for the bad scenario to allow to exit out of bad blobs

Author: eduardoramirez

hollow/src/main/java/com/netflix/hollow/core/read/engine/map/HollowMapDeltaApplicator.java

@@ -61,9 +61,14 @@ public void applyDelta() {
         target.bitsPerMapPointer = delta.bitsPerMapPointer;
         target.bitsPerMapSizeValue = delta.bitsPerMapSizeValue;
         target.bitsPerKeyElement = delta.bitsPerKeyElement;
-        target.bitsPerValueElement = delta.bitsPerValueElement;
+        // Prior to Jan 2025, the producer was able to generate blobs where it reserved 0 bits for the
+        // Map value element when all keys stored records referencing ordinal 0. In this case, when reading
+        // the value of the last bucket, the code would trigger ArrayIndexOutOfBoundsException since there
+        // no space reserved for the value element. This is a workaround to avoid the exception when
+        // transitioning from one of these bad blobs.
+        target.bitsPerValueElement = delta.bitsPerValueElement == 0 ? 1 : delta.bitsPerValueElement;
         target.bitsPerFixedLengthMapPortion = delta.bitsPerFixedLengthMapPortion;
-        target.bitsPerMapEntry = delta.bitsPerMapEntry;
+        target.bitsPerMapEntry = target.bitsPerKeyElement + target.bitsPerValueElement;
         target.emptyBucketKeyValue = delta.emptyBucketKeyValue;
         target.totalNumberOfBuckets = delta.totalNumberOfBuckets;
 
@@ -143,7 +148,15 @@ private void mergeOrdinal(int ordinal) {
             if(!removeData) {
                 for(long bucketIdx=currentFromStateStartBucket; bucketIdx<fromDataEndBucket; bucketIdx++) {
                     long bucketKey = from.entryData.getElementValue(bucketIdx * from.bitsPerMapEntry, from.bitsPerKeyElement);
-                    long bucketValue = from.entryData.getElementValue(bucketIdx * from.bitsPerMapEntry + from.bitsPerKeyElement, from.bitsPerValueElement);
+                    // Prior to Jan 2025, the producer was able to generate blobs where it reserved 0 bits for the
+                    // Map value element when all keys stored records referencing ordinal 0. In this case, when reading
+                    // the value of the last bucket, the code would trigger ArrayIndexOutOfBoundsException since there
+                    // no space reserved for the value element. This is a workaround to avoid the exception when
+                    // transitioning from one of these bad blobs.
+                    long bucketValue =
+                      from.bitsPerValueElement == 0
+                        ? 0
+                        : from.entryData.getElementValue(bucketIdx * from.bitsPerMapEntry + from.bitsPerKeyElement, from.bitsPerValueElement);
                     if(bucketKey == from.emptyBucketKeyValue)
                         bucketKey = target.emptyBucketKeyValue;
                     long currentWriteStartBucketBit = currentWriteStartBucket * target.bitsPerMapEntry;