update database to be strict and fix migration

database/migrations/2018_04_25_090031_create_setting_suppliers_table.php

@@ -17,7 +17,7 @@ class CreateSettingSuppliersTable extends Migration
             $table->increments('id');
             $table->string('company_name');
             $table->string('gst_no');
-            $table->string('supplier_reg_no');
+            $table->string('supplier_reg_no')->nullable();
             $table->string('bank_name');
             $table->string('acc_no');
             $table->timestamps();

database/migrations/2018_06_27_081455_add_bookingid_foreignkey_to_chinabankslip_table.php

@@ -15,7 +15,7 @@ class AddBookingidForeignkeyToChinabankslipTable extends Migration
     {
         Schema::table('china_bank_slips', function($table)
         {
-            $table->integer('booking_id')->unsigned();
+            $table->integer('booking_id')->unsigned()->nullable();
             $table->foreign('booking_id')->references('id')->on('bookings');
         });
     }