Bugfix #4460

Compositor:
The option to re-render a single node, didn't free memory if nodes were in
use showing exactly same RenderLayer.

source/blender/blenkernel/intern/node.c

@@ -1414,6 +1414,12 @@ void NodeTagChanged(bNodeTree *ntree, bNode *node)
 			if(sock->ns.data) {
 				free_compbuf(sock->ns.data);
 				sock->ns.data= NULL;
+				
+				if(node->preview && node->preview->rect) {
+					MEM_freeN(node->preview->rect);
+					node->preview->rect= NULL;
+				}
+					
 			}
 		}
 		node->need_exec= 1;

source/blender/src/editnode.c

@@ -284,6 +284,7 @@ static void composit_node_event(SpaceNode *snode, short event)
 			bNode *node= BLI_findlink(&snode->edittree->nodes, event-B_NODE_EXEC);
 			if(node) {
 				NodeTagChanged(snode->edittree, node);
+				NodeTagIDChanged(snode->nodetree, node->id);	/* Scene-layer nodes, texture nodes, image nodes, all can be used many times */
 				
 				/* not the best implementation of the world... but we need it to work now :) */
 				if(node->type==CMP_NODE_R_LAYERS && node->custom2) {