Fix migrations

ems-core/src/main/java/it/integry/ems/migration/_base/BaseMigration.java

@@ -213,7 +213,8 @@ public abstract class BaseMigration implements MigrationModelInterface {
     }
 
     protected void dropTable(String tableName) throws SQLException, IOException {
-        String dropSql = "DROP TABLE " + tableName;
+        String dropSql = "IF EXISTS (SELECT * FROM SYSOBJECTS WHERE id = object_id('" + tableName + "'))\r\n" +
+                "DROP TABLE " + tableName;
         executeStatement(dropSql);
     }