Merge branch 'zmoore/dispatch-strategy' of github.com:zsmoore/java-dataloader into zmoore/dispatch-strategy

Author: zsmoore

src/main/java/org/dataloader/strategy/BreadthFirstChainedDispatchStrategy.java

@@ -120,6 +120,12 @@ public Builder(ScheduledExecutorService scheduledExecutorService) {
         }
 
         public Builder setFallbackTimeout(Duration fallbackTimeout) {
+            if (fallbackTimeout == null) {
+                throw new IllegalArgumentException("fallbackTimeout must not be null");
+            }
+            if (fallbackTimeout.isZero() || fallbackTimeout.isNegative()) {
+                throw new IllegalArgumentException("fallbackTimeout must be a positive duration");
+            }
             this.fallbackTimeout = Assertions.nonNull(fallbackTimeout);
             return this;
         }