Panic will be caused when the column's comment value is one string

[dorlolo]

Description

Main problem is the function MigrateColumn in file migrator.go ,

func (m Migrator) MigrateColumn(value interface{}, field *schema.Field, columnType gorm.ColumnType) error {
    //....
    //....
    comment := field.Comment
    if comment != "" {
	    comment = comment[1 : len(comment)-1]
    }
    //....
}

excample,when the comment value is 'h' or one space, comment = comment[1 : len(comment)-1] become comment = comment[1 : 0] ,so it wuill be caused panic