Noticed when reviewing https://github.com/openjdk/jfx/pull/1394

Incorrectly set duration in the application stylesheet causes exception to be thrown each time the tooltip is shown.

To reproduce:
1. run the attached code
2. press [Set 1 (incorrect)] button
3. hover over the content area for the tooltip to appear (may need to try two times due to JDK-8296387)
4. notice the exception in stderr
5. press [Set 1s (correct)] button to set the correct value
6. hover again - each time the tooltip is about to appear, the exception is still being thrown.

It looks like css parser sets a double value to a duration property, which breaks any further attempts to rectify the problem by re-loading correct css.
We get no exception for a boolean value: -fx-wrap-text:"yo"; nor for a double value like .tooltip { -fx-graphic-text-gap:"true"; }. The latter will correctly issue a warning:
WARNING: Failed to set css [-fx-graphic-text-gap] on [DoubleProperty [bean: javafx.scene.control.Tooltip@468235b3, name: graphicTextGap, value: 4.0]] due to 'class java.lang.Boolean cannot be cast to class java.lang.Number (java.lang.Boolean and java.lang.Number are in module java.base of loader 'bootstrap')'


```
Exception in thread "JavaFX Application Thread" java.lang.ClassCastException: class java.lang.Double cannot be cast to class javafx.util.Duration (java.lang.Double is in module java.base of loader 'bootstrap'; javafx.util.Duration is in module javafx.base of loader 'app')
at javafx.controls/javafx.scene.control.Tooltip.getShowDelay(Tooltip.java:334)
at javafx.controls/javafx.scene.control.Tooltip$TooltipBehavior.lambda$0(Tooltip.java:1015)
at javafx.base/com.sun.javafx.event.CompositeEventHandler$NormalEventHandlerRecord.handleBubblingEvent(CompositeEventHandler.java:247)
at javafx.base/com.sun.javafx.event.CompositeEventHandler.dispatchBubblingEvent(CompositeEventHandler.java:80)
at javafx.base/com.sun.javafx.event.EventHandlerManager.dispatchBubblingEvent(EventHandlerManager.java:232)
at javafx.base/com.sun.javafx.event.EventHandlerManager.dispatchBubblingEvent(EventHandlerManager.java:189)
at javafx.base/com.sun.javafx.event.CompositeEventDispatcher.dispatchBubblingEvent(CompositeEventDispatcher.java:59)
at javafx.base/com.sun.javafx.event.BasicEventDispatcher.dispatchEvent(BasicEventDispatcher.java:58)
at javafx.base/com.sun.javafx.event.EventDispatchChainImpl.dispatchEvent(EventDispatchChainImpl.java:114)
at javafx.base/com.sun.javafx.event.BasicEventDispatcher.dispatchEvent(BasicEventDispatcher.java:56)
at javafx.base/com.sun.javafx.event.EventDispatchChainImpl.dispatchEvent(EventDispatchChainImpl.java:114)
at javafx.base/com.sun.javafx.event.BasicEventDispatcher.dispatchEvent(BasicEventDispatcher.java:56)
at javafx.base/com.sun.javafx.event.EventDispatchChainImpl.dispatchEvent(EventDispatchChainImpl.java:114)
at javafx.base/com.sun.javafx.event.EventUtil.fireEventImpl(EventUtil.java:74)
at javafx.base/com.sun.javafx.event.EventUtil.fireEvent(EventUtil.java:54)
at javafx.base/javafx.event.Event.fireEvent(Event.java:199)
at javafx.graphics/javafx.scene.Scene$MouseHandler.process(Scene.java:3987)
at javafx.graphics/javafx.scene.Scene.processMouseEvent(Scene.java:1893)
at javafx.graphics/javafx.scene.Scene$ScenePeerListener.mouseEvent(Scene.java:2711)
at javafx.graphics/com.sun.javafx.tk.quantum.GlassViewEventHandler$MouseEventNotification.run(GlassViewEventHandler.java:411)
at javafx.graphics/com.sun.javafx.tk.quantum.GlassViewEventHandler$MouseEventNotification.run(GlassViewEventHandler.java:1)
at java.base/java.security.AccessController.doPrivileged(AccessController.java:400)
at javafx.graphics/com.sun.javafx.tk.quantum.GlassViewEventHandler.lambda$2(GlassViewEventHandler.java:450)
at javafx.graphics/com.sun.javafx.tk.quantum.QuantumToolkit.runWithoutRenderLock(QuantumToolkit.java:430)
at javafx.graphics/com.sun.javafx.tk.quantum.GlassViewEventHandler.handleMouseEvent(GlassViewEventHandler.java:449)
at javafx.graphics/com.sun.glass.ui.View.handleMouseEvent(View.java:551)
at javafx.graphics/com.sun.glass.ui.View.notifyMouse(View.java:937)
at javafx.graphics/com.sun.glass.ui.mac.MacView.notifyMouse(MacView.java:128)
```