Targets are added to the terminal filter in GPUImageFilterGroup, so c…

…alling "targets" on this class should return the terminal filter's targets array. Currently GPUImageFilterGroup's superclass responds to this method, which returns an empty array.

framework/Source/GPUImageFilterGroup.m

@@ -73,6 +73,11 @@ - (void)removeAllTargets;
     [_terminalFilter removeAllTargets];
 }
 
+- (NSArray *)targets;
+{
+    return [_terminalFilter targets];
+}
+
 - (void)setFrameProcessingCompletionBlock:(void (^)(GPUImageOutput *, CMTime))frameProcessingCompletionBlock;
 {
     [_terminalFilter setFrameProcessingCompletionBlock:frameProcessingCompletionBlock];