SnapdragonGallery: update min birghtness value

update min birghtness value, 0.0f is not support

Change-Id: I6423dab0e882187ef6e1a8d670efaad04dc80fc7
diff --git a/src/com/android/gallery3d/app/GestureControllerOverlay.java b/src/com/android/gallery3d/app/GestureControllerOverlay.java
index efed3e9..9060490 100755
--- a/src/com/android/gallery3d/app/GestureControllerOverlay.java
+++ b/src/com/android/gallery3d/app/GestureControllerOverlay.java
@@ -220,7 +220,7 @@
         }
         float targetBrightness = (float) (mStartBrightness + adjustPercent * 1.0f);
         if (targetBrightness <= 0.0f) {
-            targetBrightness = 0.0f;
+            targetBrightness = 0.004f;
         } else if (targetBrightness >= 1.0f) {
             targetBrightness = 1.0f;
         }