Filter out empty region names

We drop any region names where `name.isBlank()` is true.  Specifically,
an empty or missing region attribute will not result in us trying to
filter with an empty region name.

Fixes #36

optimiser-controller/src/main/java/eu/nebulouscloud/optimiser/controller/NebulousApp.java

@@ -313,7 +313,9 @@ public NebulousApp(JsonNode app_message, String kubevela_string, ExnConnector ex
             .filter((c) -> c.at("/enabled").asBoolean())
             .collect(Collectors.toMap(
                 (c) -> c.at("/uuid").asText(),
-                (c) -> Arrays.stream(c.at("/regions").asText().split(",")).collect(Collectors.toSet())));
+                (c) -> Arrays.stream(c.at("/regions").asText().split(","))
+                    .filter(regionName -> !regionName.isBlank())
+                    .collect(Collectors.toSet())));
         if (clouds.isEmpty()) {
             log.error("No enabled clouds given in app creation message, setting app status to FAILED and aborting deployment.");
             this.setStateFailed();