fix issues relating to race conditions where draftTx does not exist (#15420)

* fix issues relating to race conditions where draftTx does not exist

* add another fail safe for inflight initializations

ui/ducks/send/send.js

@@ -603,7 +603,7 @@ export const initializeSendState = createAsyncThunk(
     // For instance, in the actions.js file we dispatch this action anytime the
     // chain changes.
     if (!draftTransaction) {
-      thunkApi.rejectWithValue(
+      return thunkApi.rejectWithValue(
         'draftTransaction not found, possibly not on send flow',
       );
     }
@@ -678,6 +678,20 @@ export const initializeSendState = createAsyncThunk(
     // We have to keep the gas slice in sync with the send slice state
     // so that it'll be initialized correctly if the gas modal is opened.
     await thunkApi.dispatch(setCustomGasLimit(gasLimit));
+
+    // There may be a case where the send has been canceled by the user while
+    // the gas estimate is being computed. So we check again to make sure that
+    // a currentTransactionUUID exists and matches the previous tx.
+    const newState = thunkApi.getState();
+    if (
+      newState.send.currentTransactionUUID !== sendState.currentTransactionUUID
+    ) {
+      return thunkApi.rejectWithValue(
+        `draftTransaction changed during initialization.
+        A new initializeSendState action must be dispatched.`,
+      );
+    }
+
     return {
       account,
       chainId: getCurrentChainId(state),
@@ -1396,6 +1410,7 @@ const slice = createSlice({
     validateSendState: (state) => {
       const draftTransaction =
         state.draftTransactions[state.currentTransactionUUID];
+      if (draftTransaction) {
         switch (true) {
           case Boolean(draftTransaction.amount.error):
           case Boolean(draftTransaction.gas.error):
@@ -1419,6 +1434,7 @@ const slice = createSlice({
           default:
             draftTransaction.status = SEND_STATUSES.VALID;
         }
+      }
     },
   },
   extraReducers: (builder) => {
@@ -1512,15 +1528,9 @@ const slice = createSlice({
         state.selectedAccount.balance = action.payload.account.balance;
         const draftTransaction =
           state.draftTransactions[state.currentTransactionUUID];
+        if (draftTransaction) {
           draftTransaction.gas.gasLimit = action.payload.gasLimit;
-        slice.caseReducers.updateGasFeeEstimates(state, {
-          payload: {
-            gasFeeEstimates: action.payload.gasFeeEstimates,
-            gasEstimateType: action.payload.gasEstimateType,
-          },
-        });
           draftTransaction.gas.gasTotal = action.payload.gasTotal;
-        state.gasEstimatePollToken = action.payload.gasEstimatePollToken;
           if (action.payload.chainHasChanged) {
             // If the state was reinitialized as a result of the user changing
             // the network from the network dropdown, then the selected asset is
@@ -1532,6 +1542,14 @@ const slice = createSlice({
               state.selectedAccount.balance;
             draftTransaction.asset.details = null;
           }
+        }
+        slice.caseReducers.updateGasFeeEstimates(state, {
+          payload: {
+            gasFeeEstimates: action.payload.gasFeeEstimates,
+            gasEstimateType: action.payload.gasEstimateType,
+          },
+        });
+        state.gasEstimatePollToken = action.payload.gasEstimatePollToken;
         if (action.payload.gasEstimatePollToken) {
           state.gasEstimateIsLoading = false;
         }
@@ -2641,7 +2659,11 @@ export function isSendStateInitialized(state) {
  * @type {Selector<boolean>}
  */
 export function isSendFormInvalid(state) {
-  return getCurrentDraftTransaction(state).status === SEND_STATUSES.INVALID;
+  const draftTransaction = getCurrentDraftTransaction(state);
+  if (!draftTransaction) {
+    return true;
+  }
+  return draftTransaction.status === SEND_STATUSES.INVALID;
 }
 
 /**