Display: Make sure the next displayable has a return if is an Alert

Some jars create an Alert and set it as the next Displayable without
using the specific method for Alerts. So treat those cases.

src/javax/microedition/lcdui/Alert.java

@@ -218,6 +218,10 @@ else if ((key == Canvas.DOWN || key == Canvas.KEY_NUM8) && scrollY < maxScroll)
 		{
 			scrollY = Math.min(maxScroll, scrollY + scrollAmount);
 		}
+		else if((key == Canvas.FIRE || key == Canvas.KEY_NUM5))
+		{
+			defaultListener.commandAction(DISMISS_COMMAND, nextScreen);
+		}
 
 		if (handled) { _invalidate(); }
 

src/javax/microedition/lcdui/Display.java

@@ -162,7 +162,7 @@ public void setCurrent(Displayable next)
 					next.showNotify();
 				} 
 				finally { isSettingCurrent = false; }
-
+				if(next instanceof Alert) { ((Alert) next).setNextScreen(current); }
 				current = next;
 				current.notifySetCurrent();
 				Mobile.getPlatform().flushGraphics(current.platformImage, 0,0, current.width, current.height);