I cant delete record of table having Primary Key

Model:

Ext.define('InventoryList_M', {
extend: 'Ext.data.Model',
config: {
fields: [
{name:'inventoryID',type : 'int', fieldOption : 'PRIMARY KEY ASC'},
{name:'StartTime',type:'string'},
{name:'EndTime',type:'string'},
{name:'Days',type:'string'},
{name:'ProgramName',type:'string'}
],
proxy: {
type: 'sqlitestorage',
dbConfig: {
tablename: 'tblInventoryList',
dbConn: WOTabletOrders.util.InitSQLite.getConnection()
}
}
}
});
Store:

Ext.define('InventoryList_S', {
extend: 'Ext.data.Store',
requires: ['InventoryList_M'],
config: {
model: 'WOTabletOrders.model.InventoryList_M',
autoLoad: true,
storeId: 'storeInventoryList'
}
});

Code:
var objStore=list.getStore();
var rec=objStore.getAt(index);
objStore.remove(rec);
objStore.sync();
Got an error:
undefined----could not execute statement (19 constraint failed)

Please Help Thanks in advance