Do not process missing index types (#1985)

Fixes an error that arises, when a plugin with search
indices for repositories is removed and later on a repository
is deleted. This led to a null pointer exception in the
SearchableTypeResolver, but only because an "illegal" index
detail without proper type was given as a parameter. This
type cannot be resolved any longer due to the removed plugin.
We therefore can simply filter these index details.

scm-webapp/src/main/java/sonia/scm/search/LuceneSearchEngine.java

@@ -27,6 +27,8 @@ package sonia.scm.search;
 import com.google.common.base.Joiner;
 import org.apache.shiro.SecurityUtils;
 import org.apache.shiro.subject.Subject;
+import org.slf4j.Logger;
+import org.slf4j.LoggerFactory;
 import sonia.scm.work.CentralWorkQueue;
 import sonia.scm.work.CentralWorkQueue.Enqueue;
 import sonia.scm.work.Task;
@@ -41,6 +43,8 @@ import java.util.stream.Collectors;
 
 public class LuceneSearchEngine implements SearchEngine {
 
+  private static final Logger LOG = LoggerFactory.getLogger(LuceneSearchEngine.class);
+
   private final IndexManager indexManager;
   private final SearchableTypeResolver resolver;
   private final LuceneQueryBuilderFactory queryBuilderFactory;
@@ -128,10 +132,19 @@ public class LuceneSearchEngine implements SearchEngine {
       indexManager.all()
         .stream()
         .filter(predicate)
+        .filter(this::isTypeAvailable)
         .map(details -> new IndexParams(details.getName(), resolver.resolve(details.getType())))
         .forEach(consumer);
     }
 
+    private boolean isTypeAvailable(IndexDetails details) {
+      if (details.getType() == null) {
+        LOG.info("no type found for index with name '{}'; index will not be updated", details.getName());
+        return false;
+      }
+      return true;
+    }
+
     private void batch(IndexParams params, Task task) {
       LuceneSearchEngine.this.enqueue(params.getSearchableType(), params.getIndex(), resources, task);
     }

scm-webapp/src/main/java/sonia/scm/search/SearchableTypeResolver.java

@@ -86,9 +86,6 @@ class SearchableTypeResolver {
   }
 
   public LuceneSearchableType resolve(Class<?> type) {
-    if (type == null) {
-      throw notFound(entity("type", "null"));
-    }
     LuceneSearchableType searchableType = classToSearchableType.get(type);
     if (searchableType == null) {
       throw notFound(entity("type", type.getName()));