fix: fix search_kernel command (#3157)

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## Description
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The search-kernel command in the base_node UI currently returns either an error, none or the block containing said kernel. 
The UI interprets a None as a successful command, but the block could not be found due to it being a pruned block. This is incorrect, as the returned block is always a `historical block`. `Historical blocks` can have pruned outputs in them. So when a block is pruned, the base_node will return the block with the information it can fill in, plus all pruned outputs. 

When a kernel is not found in the chain, the search commands returns Ok(None) and the UI now interprets this correctly as the kernel is not found. 

## Motivation and Context
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## Checklist:
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* [x] I'm merging against the `development` branch.
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applications/tari_base_node/src/command_handler.rs

@@ -325,11 +325,8 @@ impl CommandHandler {
                     );
                 },
                 Ok(mut data) => match data.pop() {
-                    Some(v) => println!("{}", v.block()),
-                    _ => println!(
-                        "Pruned node: kernel found, but block not found for kernel signature {}",
-                        hex_sig
-                    ),
+                    Some(v) => println!("{}", v),
+                    _ => println!("No kernel with signature {} found", hex_sig),
                 },
             };
         });