several small changes

jme3-core/src/main/java/com/jme3/renderer/GeometryRenderHandler.java

@@ -43,7 +43,7 @@ public interface GeometryRenderHandler {
     /**
      * Default implementation that renders the geometry and returns true.
      */
-    public static final GeometryRenderHandler DEFAULT = (rm, geom) -> {
+    GeometryRenderHandler DEFAULT = (rm, geom) -> {
         rm.renderGeometry(geom);
         return true;
     };

jme3-core/src/main/java/com/jme3/renderer/RenderManager.java

@@ -187,7 +187,7 @@ public <T extends PipelineContext> T getOrCreateContext(Class<T> type, Supplier<
         T c = getContext(type);
         if (c == null) {
             c = supplier.get();
-            contexts.put(type, c);
+            registerContext(type, c);
         }
         return c;
     }

jme3-core/src/main/java/com/jme3/texture/FrameBuffer.java

@@ -267,18 +267,27 @@ public void addColorTarget(FrameBufferTextureTarget colorBuf){
     }
 
     /**
-     * Sets the color target at the index.
+     * Replaces the color target at the index.
+     * <p>
+     * A color target must already exist at the index, otherwise
+     * an exception will be thrown.
      * 
-     * @param i
-     * @param colorBuf 
+     * @param i index of color target to replace
+     * @param colorBuf color target to replace with
      */
-    public void setColorTarget(int i, FrameBufferTextureTarget colorBuf) {
+    public void replaceColorTarget(int i, FrameBufferTextureTarget colorBuf) {
+        if (i < 0 || i >= colorBufs.size()) {
+            throw new IndexOutOfBoundsException("No color target exists to replace at index=" + i);
+        }
         colorBuf.slot = i;
         colorBufs.set(i, colorBuf);
     }
 
     /**
      * Removes the color target at the index.
+     * <p>
+     * Color targets above the removed target will have their
+     * slot indices shifted accordingly.
      * 
      * @param i 
      */