Fix migrations

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

@@ -213,9 +213,11 @@ public abstract class BaseMigration implements MigrationModelInterface {
     }
 
     protected void dropTable(String tableName) throws SQLException, IOException {
+        if (existsTable(tableName)) {
             String dropSql = "DROP TABLE " + tableName;
             executeStatement(dropSql);
         }
+    }
 
     protected void createSetupQuery(String codQuery, String name, String query) throws SQLException, IOException {
         if (UtilityString.isNullOrEmpty(codQuery)) {