fix problem where the screen is sometimes all black in recovery

Change-Id: Ifa0b59e43eaf0bea9435aa4d96c5b0fc4f10fbfe
diff --git a/minui/graphics.c b/minui/graphics.c
index fa8e510..de1cfdf 100644
--- a/minui/graphics.c
+++ b/minui/graphics.c
@@ -336,6 +336,9 @@
     gl->enable(gl, GGL_BLEND);
     gl->blendFunc(gl, GGL_SRC_ALPHA, GGL_ONE_MINUS_SRC_ALPHA);
 
+    gr_fb_blank(true);
+    gr_fb_blank(false);
+
     return 0;
 }