minor recovery fixes

- protect against missing/malformed bitmaps: fail to display them but
  don't crash.

- don't draw animation overlays until the overlay offset is computed.

- logging cleanup

Change-Id: Ieb1c155cfbb11e643000bdb5d1a57900c8757739
diff --git a/minui/graphics.c b/minui/graphics.c
index 88572a8..287878e 100644
--- a/minui/graphics.c
+++ b/minui/graphics.c
@@ -245,6 +245,9 @@
 }
 
 void gr_texticon(int x, int y, gr_surface icon) {
+    if (gr_context == NULL || icon == NULL) {
+        return;
+    }
     GGLContext* gl = gr_context;
 
     gl->bindTexture(gl, (GGLSurface*) icon);
@@ -268,7 +271,7 @@
 }
 
 void gr_blit(gr_surface source, int sx, int sy, int w, int h, int dx, int dy) {
-    if (gr_context == NULL) {
+    if (gr_context == NULL || source == NULL) {
         return;
     }
     GGLContext *gl = gr_context;