Merge pull request #1698 from h2database/test-crash-api-npe

TestCrashAPI-NPE

h2/src/main/org/h2/engine/Database.java

@@ -1082,10 +1082,12 @@ public class Database implements DataHandler {
      * @param session the session
      */
     public void unlockMeta(Session session) {
+        if (meta != null) {
             unlockMetaDebug(session);
             meta.unlock(session);
             session.unlock(meta);
         }
+    }
 
     /**
      * This method doesn't actually unlock the metadata table, all it does it
@@ -1888,7 +1890,7 @@ public class Database implements DataHandler {
                 }
             }
         } else {
-            lockMeta(session);
+            boolean metaWasLocked = lockMeta(session);
             synchronized (this) {
                 int id = obj.getId();
                 removeMeta(session, id);
@@ -1898,6 +1900,9 @@ public class Database implements DataHandler {
                     objectIds.set(id);
                 }
             }
+            if (!metaWasLocked) {
+                unlockMeta(session);
+            }
         }
     }