Remove Slice setAttribute zero-length-array check

Slices' optional tags follow the rules for BAM tagged fields, so
zero-length 'B' arrays are valid. Slice tags are currently unused,
so the question is somewhat moot and there are no test cases.

src/main/java/htsjdk/samtools/cram/structure/Slice.java

@@ -745,9 +745,6 @@ public void setReferenceMD5(final CRAMReferenceRegion cramReferenceRegion) {
      * @param value tag value
      */
     public void setAttribute(final String tag, final Object value) {
-        if (value != null && value.getClass().isArray() && Array.getLength(value) == 0) {
-            throw new IllegalArgumentException("Empty value passed for tag " + tag);
-        }
         setAttribute(SAMTag.makeBinaryTag(tag), value);
     }