Fix Wave Machine default amplitude

Got set to `0` somehow in the NL7 updates.

Author: LaCuneta

Sample Models/Chemistry & Physics/Waves/Wave Machine.nlogox

@@ -108,7 +108,7 @@ end
     <slider x="265" step="1" y="200" max="11" width="250" display="driver-y" height="50" min="-11" direction="Horizontal" default="0.0" variable="driver-y"></slider>
     <slider x="138" step="1" y="310" max="100" width="250" display="driver-frequency" height="50" min="0" direction="Horizontal" default="100.0" variable="driver-frequency"></slider>
     <slider x="10" step="1" y="255" max="10" width="250" display="driver-size" height="50" min="0" direction="Horizontal" default="2.0" variable="driver-size"></slider>
-    <slider x="265" step="1" y="255" max="30" width="250" display="driver-amplitude" height="50" min="0" direction="Horizontal" default="0.0" variable="driver-amplitude"></slider>
+    <slider x="265" step="1" y="255" max="30" width="250" display="driver-amplitude" height="50" min="0" direction="Horizontal" default="9.0" variable="driver-amplitude"></slider>
     <slider x="10" step="1" y="115" max="50" width="250" display="stiffness" height="50" min="0" direction="Horizontal" default="50.0" variable="stiffness"></slider>
     <slider x="265" step="1" y="115" max="99" width="250" display="friction" height="50" min="0" direction="Horizontal" default="10.0" variable="friction"></slider>
     <slider x="135" step="1" y="395" max="90" width="250" display="view-angle" height="50" min="0" direction="Horizontal" default="45.0" variable="view-angle"></slider>