Backport "Skip adding history entry for empty txMeta diffs (#8379)"

This backports #8379.

CHANGELOG.md

@@ -4,6 +4,7 @@
 
 ## 7.7.9 Tue Apr 28 2020
 - [#8446](https://github.com/MetaMask/metamask-extension/pull/8446): Fix popup not opening
+- [#8449](https://github.com/MetaMask/metamask-extension/pull/8449): Skip adding history entry for empty txMeta diffs
 
 ## 7.7.8 Wed Mar 11 2020
 - [#8176](https://github.com/MetaMask/metamask-extension/pull/8176): Handle and set gas estimation when max mode is clicked

app/scripts/controllers/transactions/tx-state-manager.js

@@ -195,7 +195,9 @@ class TransactionStateManager extends EventEmitter {
     const previousState = txStateHistoryHelper.replayHistory(txMeta.history)
     // generate history entry and add to history
     const entry = txStateHistoryHelper.generateHistoryEntry(previousState, currentState, note)
-    txMeta.history.push(entry)
+    if (entry.length) {
+      txMeta.history.push(entry)
+    }
 
     // commit txMeta to state
     const txId = txMeta.id

test/unit/app/controllers/transactions/tx-state-manager-test.js

@@ -252,6 +252,23 @@ describe('TransactionStateManager', function () {
       assert.deepEqual(result.history[1][0].value, expectedEntry.value, 'two history items (initial + diff) value')
       assert.ok(result.history[1][0].timestamp >= before && result.history[1][0].timestamp <= after)
     })
+
+    it('does NOT add empty history items', function () {
+      const txMeta = {
+        id: '1',
+        status: 'unapproved',
+        metamaskNetworkId: currentNetworkId,
+        txParams: {
+          gasPrice: '0x01',
+        },
+      }
+
+      txStateManager.addTx(txMeta)
+      txStateManager.updateTx(txMeta)
+
+      const { history } = txStateManager.getTx('1')
+      assert.equal(history.length, 1, 'two history items (initial + diff)')
+    })
   })
 
   describe('#getUnapprovedTxList', function () {