Merge pull request #454 from kfrajer/master

Fixes #442: NPE when calling background(PIamge)

Author: codeanticode

core/src/processing/opengl/PGraphicsOpenGL.java

@@ -5792,6 +5792,7 @@ protected void setImpl(PImage sourceImage,
 
     // Copies the pixels
     loadPixels();
+    if(sourceImage.pixels==null) sourceImage.loadPixels();
     int sourceOffset = sourceY * sourceImage.pixelWidth + sourceX;
     int targetOffset = targetY * pixelWidth + targetX;
     for (int y = sourceY; y < sourceY + sourceHeight; y++) {