Fixes Desaturate Feeding back into the previous step

This was caused by not copying the input to the output
and just simply assigning the value of the input to the
output.

Closes #252

Author: JLLeitschuh

core/src/main/java/edu/wpi/grip/core/operations/composite/DesaturateOperation.java

@@ -54,7 +54,7 @@ public void perform(InputSocket<?>[] inputs, OutputSocket<?>[] outputs) {
         switch (input.channels()) {
             case 1:
                 // If the input is already one channel, it's already desaturated
-                output = input;
+                input.copyTo(output);
                 break;
 
             case 3: