Merge #1509: export transactions: output a blank if fee is 0

b1736bbd404df91a0150c06985998ac1575c317d export transactions: output a blank if fee is 0 (pythcoiner)

Pull request description:

  This PR replace the fee displayed as 0 by a blank.

ACKs for top commit:
  jp1ac4:
    Tested ACK b1736bbd404df91a0150c06985998ac1575c317d.

Tree-SHA512: 02d132b5de988e0f8b0c3ad6ec463c0a70f9d207b0620560ab1fb683b3729f96bc044d6f4315dc0f48eea4ddb6142ea60141e1cb430c879f2e177eb3a549ee9a

liana-gui/src/export.rs

@@ -305,6 +305,11 @@ impl State {
                     let value = value as f64 / 100_000_000.0;
                     let fee = fee as f64 / 100_000_000.0;
                     let block = tx.height.map(|h| h.to_string()).unwrap_or("".to_string());
+                    let fee = if fee != 0.0 {
+                        fee.to_string()
+                    } else {
+                        "".into()
+                    };
 
                     let line = format!(
                         "{},{},{},{},{},{}\n",