Bug 182190 [StatusHandling] [Wizards] getControl assert on wizard page has no message
M6 If you forget to set the control on your wizard page our assert gives no feedback. We need an error message.
bundles/org.eclipse.jface/src/org/eclipse/jface/wizard/WizardDialog.java
restoreUIState(state);
            cancelButton.addSelectionListener(cancelListener);
            setDisplayCursor(null);
            cancelButton.setCursor(null);
            waitCursor.dispose();
            waitCursor = null;
            arrowCursor.dispose();
            arrowCursor = null;
            Control focusControl = (Control) state.get(FOCUS_CONTROL);
            if (focusControl != null) {
				focusControl.setFocus();
			}
        }
    }
    /**
     * Updates this dialog's controls to reflect the current page.
     */
    protected void update() {
        
        updateWindowTitle();
        
        updateTitleBar();
        
        updateButtons();
        
		
		firePageChanged(new PageChangedEvent(this, getCurrentPage()));
    }
    /* (non-Javadoc)
     * Method declared on IWizardContainer.