Merge branch 'rate-service-edits' into 'main'

Skipping empty rate contributors

See merge request !443

src/main/java/gov/usgs/earthquake/nshmp/calc/EqRate.java

@@ -146,13 +146,16 @@ public class EqRate {
         treeMfd.add(rupturesMfd);
       }
 
-      Contributor contrib = new Contributor(
-          tree.name(),
-          tree.id(),
-          tree.setting(),
-          tree.type(),
-          treeMfd.build().values());
-      mfds.add(contrib);
+      XySequence mfd = treeMfd.build().values();
+      if (!mfd.isClear()) {
+        Contributor contrib = new Contributor(
+            tree.name(),
+            tree.id(),
+            tree.setting(),
+            tree.type(),
+            mfd);
+        mfds.add(contrib);
+      }
     }
 
     /* Compute total and convert to sequences. */