ONOS-6081 Do not throw Exception when queried for unknown resource.

Change-Id: I3b5c7306350c8f175e809e41611b5cabb844fe92
diff --git a/core/store/dist/src/main/java/org/onosproject/store/resource/impl/ConsistentContinuousResourceSubStore.java b/core/store/dist/src/main/java/org/onosproject/store/resource/impl/ConsistentContinuousResourceSubStore.java
index 60eed40..887b35b 100644
--- a/core/store/dist/src/main/java/org/onosproject/store/resource/impl/ConsistentContinuousResourceSubStore.java
+++ b/core/store/dist/src/main/java/org/onosproject/store/resource/impl/ConsistentContinuousResourceSubStore.java
@@ -94,11 +94,12 @@
             return false;
         }
 
-        ContinuousResource registered = children.value().stream()
+        boolean notEnoughRegistered = children.value().stream()
                 .filter(c -> c.id().equals(resource.id()))
                 .findFirst()
-                .get();
-        if (registered.value() < resource.value()) {
+                .map(registered -> registered.value() < resource.value())
+                .orElse(true);
+        if (notEnoughRegistered) {
             // Capacity < requested, can never satisfy
             return false;
         }