prevent unwrap(), poisoned data

lib/src/lightwallet.rs

@@ -1470,26 +1470,43 @@ pub fn scan_full_tx(&self, tx: &Transaction, height: i32, datetime: u64) {
                         // Do it in a short scope because of the write lock.
                         {
                             info!("A sapling output was sent in {}", tx.txid());
-                            let mut txs = self.txs.write().unwrap();
-                            if txs.get(&tx.txid()).unwrap().outgoing_metadata.iter()
-                                    .find(|om| om.address == address && om.value == note.value  && om.memo == memo)
-                                    .is_some() {
-                                warn!("Duplicate outgoing metadata");
-                                continue;
-                            }
+                            match self.txs.write() {
+                                Ok(mut txs) => {
+                                    match txs.get(&tx.txid()) {
+                                        Some(wtx) => {
+                                            if wtx.outgoing_metadata.iter()
+                                                .any(|om| om.address == address && om.value == note.value && om.memo == memo)
+                                            {
+                                                warn!("Duplicate outgoing metadata");
+                                                continue;
+                                            }
                             
-                            // Write the outgoing metadata
-                            txs.get_mut(&tx.txid()).unwrap()
-                                .outgoing_metadata
-                                .push(OutgoingTxMetadata{
-                                    address, value: note.value, memo,
-                                });
+                                            // Write the outgoing metadata
+                                            txs.get_mut(&tx.txid()).unwrap()
+                                                .outgoing_metadata
+                                                .push(OutgoingTxMetadata {
+                                                    address,
+                                                    value: note.value,
+                                                    memo,
+                                                });
+                                        },
+                                        None => {
+                                            error!("Can not find any entry for txid : {}", tx.txid());
+                                            continue; 
+                                        }
+                                    }
+                                },
+                                Err(poisoned) => {
+                                    error!("Lock is poisoned: {}", poisoned);
+                                    return; 
+                                }
+                            }
                         }
                     },
                     None => {}
             };
         }
-    }
+    }                            
     // Mark this Tx as scanned
     {
         let mut txs = self.txs.write().unwrap();