Fix glReadPixels() to verify that both x and y are non-negative.
diff --git a/opengl/libagl/texture.cpp b/opengl/libagl/texture.cpp
index 13d078e..89a19b6 100644
--- a/opengl/libagl/texture.cpp
+++ b/opengl/libagl/texture.cpp
@@ -1467,7 +1467,7 @@
         ogles_error(c, GL_INVALID_VALUE);
         return;
     }
-    if (x<0 || x<0) {
+    if (x<0 || y<0) {
         ogles_error(c, GL_INVALID_VALUE);
         return;
     }