Salut! Bonjour,
J'aimerais solliciter votre aide concernant mon problème. 
Voici l'erreur lors de l'exécution :

Exception in thread "AWT-EventQueue-1" java.lang.NullPointerException

at formEdit.FormEditFacture.ModifierFactureActionPerformed(FormEditFacture.java:258)

at formEdit.FormEditFacture.access$000(FormEditFacture.java:17)

at formEdit.FormEditFacture$1.actionPerformed(FormEditFacture.java:60)

at javax.swing.AbstractButton.fireActionPerformed(AbstractButton.java:2022)

at javax.swing.AbstractButton$Handler.actionPerformed(AbstractButton.java:2348)

at javax.swing.DefaultButtonModel.fireActionPerformed(DefaultButtonModel.java:402)

at javax.swing.DefaultButtonModel.setPressed(DefaultButtonModel.java:259)

at javax.swing.plaf.basic.BasicButtonListener.mouseReleased(BasicButtonListener.java:252)

at java.awt.Component.processMouseEvent(Component.java:6539)

at javax.swing.JComponent.processMouseEvent(JComponent.java:3324)

at java.awt.Component.processEvent(Component.java:6304)

at java.awt.Container.processEvent(Container.java:2239)

at java.awt.Component.dispatchEventImpl(Component.java:4889)

at java.awt.Container.dispatchEventImpl(Container.java:2297)

at java.awt.Component.dispatchEvent(Component.java:4711)

at java.awt.LightweightDispatcher.retargetMouseEvent(Container.java:4904)

at java.awt.LightweightDispatcher.processMouseEvent(Container.java:4535)

at java.awt.LightweightDispatcher.dispatchEvent(Container.java:4476)

at java.awt.Container.dispatchEventImpl(Container.java:2283)

at java.awt.Window.dispatchEventImpl(Window.java:2746)

at java.awt.Component.dispatchEvent(Component.java:4711)

at java.awt.EventQueue.dispatchEventImpl(EventQueue.java:760)

at java.awt.EventQueue.access$500(EventQueue.java:97)

at java.awt.EventQueue$3.run(EventQueue.java:709)

at java.awt.EventQueue$3.run(EventQueue.java:703)

at java.security.AccessController.doPrivileged(Native Method)

at java.security.ProtectionDomain$JavaSecurityAccessImpl.doIntersectionPrivilege(ProtectionDomain.java:74)

at java.security.ProtectionDomain$JavaSecurityAccessImpl.doIntersectionPrivilege(ProtectionDomain.java:84)

at java.awt.EventQueue$4.run(EventQueue.java:733)

at java.awt.EventQueue$4.run(EventQueue.java:731)

at java.security.AccessController.doPrivileged(Native Method)

at java.security.ProtectionDomain$JavaSecurityAccessImpl.doIntersectionPrivilege(ProtectionDomain.java:74)

at java.awt.EventQueue.dispatchEvent(EventQueue.java:730)

at org.GNOME.Accessibility.AtkWrapper$6.dispatchEvent(AtkWrapper.java:715)

at java.awt.EventDispatchThread.pumpOneEventForFilters(EventDispatchThread.java:205)

at java.awt.EventDispatchThread.pumpEventsForFilter(EventDispatchThread.java:116)

at java.awt.EventDispatchThread.pumpEventsForHierarchy(EventDispatchThread.java:105)

at java.awt.EventDispatchThread.pumpEvents(EventDispatchThread.java:101)

at java.awt.EventDispatchThread.pumpEvents(EventDispatchThread.java:93)

at java.awt.EventDispatchThread.run(EventDispatchThread.java:82)

BUILD SUCCESSFUL (total time: 24 seconds)

FormEditFacture formFacture = new FormEditFacture(this);