chore: minor changes

Author: lvca

engine/src/main/java/com/arcadedb/graph/ImmutableEdge.java

@@ -167,11 +167,15 @@ public synchronized JSONObject toJSON(final boolean includeMetadata) {
 
   @Override
   public synchronized String toString() {
-    final StringBuilder buffer = new StringBuilder();
-    buffer.append(out != null ? out.toString() : "?");
-    buffer.append("<->");
-    buffer.append(in != null ? in.toString() : "?");
-    return buffer.toString();
+    if (out == null && in == null)
+      return rid.toString();
+    else {
+      final StringBuilder buffer = new StringBuilder();
+      buffer.append(out != null ? out.toString() : "?");
+      buffer.append("<->");
+      buffer.append(in != null ? in.toString() : "?");
+      return buffer.toString();
+    }
   }
 
   @Override

engine/src/test/java/com/arcadedb/TransactionIsolationTest.java

@@ -229,7 +229,7 @@ public void testRepeatableRead() throws InterruptedException {
               assertThat(
                       database.query("sql", "select from Node where id = 0")
                               .nextIfAvailable()
-                              .<String>getProperty("modified")
+                              .<Boolean>getProperty("modified")
               ).isNull();
 
             sem3.await();
@@ -238,7 +238,7 @@ public void testRepeatableRead() throws InterruptedException {
             assertThat(
                     database.query("sql", "select from Node where id = 0")
                             .nextIfAvailable()
-                            .<String>getProperty("modified")
+                            .<Boolean>getProperty("modified")
             ).isNull();
 
           } catch (InterruptedException e) {