try to shut down in a bit more ordered way

inspired by https://github.com/yacy/yacy_search_server/issues/518

source/net/yacy/crawler/CrawlStacker.java

@@ -124,6 +124,12 @@ public final class CrawlStacker implements WorkflowTask<Request>{
     public synchronized void close() {
         CrawlStacker.log.info("Shutdown. waiting for remaining " + this.size() + " crawl stacker job entries. please wait.");
         this.requestQueue.shutdown();
+        
+        // busy waiting for the queue to empty
+        for (int i = 0; i < 10; i++) {
+        	if (this.size() <= 0) break;
+        	try {Thread.sleep(1000);} catch (InterruptedException e) {}
+        }
 
         CrawlStacker.log.info("Shutdown. Closing stackCrawl queue.");
 

source/net/yacy/search/index/Fulltext.java

@@ -366,7 +366,7 @@ public final class Fulltext {
 
     public void putDocument(final SolrInputDocument doc) throws IOException {
         final SolrConnector connector = this.getDefaultConnector();
-        if (connector == null) return;
+        if (connector == null || connector.isClosed()) return;
         final String id = (String) doc.getFieldValue(CollectionSchema.id.getSolrFieldName());
         final String url = (String) doc.getFieldValue(CollectionSchema.sku.getSolrFieldName());
         assert url != null && url.length() < 30000;

source/net/yacy/yacy.java

@@ -406,8 +406,8 @@ public final class yacy {
                 ConcurrentLog.severe("STARTUP", "Unexpected Error: " + e.getClass().getName(),e);
                 //System.exit(1);
             }
-            if(lock != null) lock.release();
+            if (lock != null && lock.isValid()) lock.release();
-            if(channel != null) channel.close();
+            if (channel != null && channel.isOpen()) channel.close();
         } catch (final Exception ee) {
             ConcurrentLog.severe("STARTUP", "FATAL ERROR: " + ee.getMessage(),ee);
         } finally {