prevent null reference exception trying to show tooltip for broken recall

src/ui/viewmodels/TriggerConditionViewModel.cpp

@@ -856,10 +856,15 @@ static void BuildRecallTooltip(std::wstring& sTooltip,
             BuildRecallTooltip(sTooltip, mRememberRef, pIter->second.first, *pIter->second.second, *pRecallOperand);
     }
 
-    sTooltip += ra::StringPrintf(L"\r\n%u: ", gsl::narrow_cast<uint32_t>(nConditionIndex + 1));
-
-    if (pOperand.value.memref->value.memref_type == RC_MEMREF_TYPE_MODIFIED_MEMREF)
+    if (!pOperand.value.memref)
+    {
+        // if memref is null, a Remember couldn't be found for the {recall}
+        sTooltip.append(L"\r\n[invalid recall]");
+    }
+    else if (pOperand.value.memref->value.memref_type == RC_MEMREF_TYPE_MODIFIED_MEMREF)
     {
+        sTooltip += ra::StringPrintf(L"\r\n%u: ", gsl::narrow_cast<uint32_t>(nConditionIndex + 1));
+
         GSL_SUPPRESS_TYPE1 const rc_modified_memref_t* combining_memref =
             reinterpret_cast<rc_modified_memref_t*>(pOperand.value.memref);
         if (combining_memref->modifier_type == RC_OPERATOR_INDIRECT_READ)
@@ -945,7 +950,7 @@ std::wstring TriggerConditionViewModel::GetRecallTooltip(bool bOperand2) const
     if (pLastRememberCondition)
         BuildRecallTooltip(sTooltip, mRememberRef, nLastRememberIndex, *pLastRememberCondition, *pOperand);
     else
-        sTooltip += L"???";
+        sTooltip += L"\r\n[invalid recall]";
 
     return sTooltip;
 }

tests/ui/viewmodels/TriggerConditionViewModel_Tests.cpp

@@ -1403,7 +1403,7 @@ TEST_CLASS(TriggerConditionViewModel_Tests)
                                       L"2: 0x00000302 & 0x000001ff -> 0x00000102\r\n"
                                       L"3: 0x00000102 * 0x00000002 -> 0x00000204\r\n"
                                       L"4: 0x00000204 + 0x00000004 -> 0x00000208"),
-            pCondition5->GetTooltip(TriggerConditionViewModel::TargetTypeProperty));
+                         pCondition5->GetTooltip(TriggerConditionViewModel::TargetTypeProperty));
         Assert::AreEqual(std::wstring(L""), pCondition5->GetTooltip(TriggerConditionViewModel::TargetValueProperty));
 
         // $0010 = 0x0000 + 0x04 + 0x0208 = 0x020c
@@ -1565,6 +1565,34 @@ TEST_CLASS(TriggerConditionViewModel_Tests)
         Assert::AreEqual(std::wstring(L"6"), pCondition10->GetTooltip(TriggerConditionViewModel::TargetValueProperty));
     }
 
+    TEST_METHOD(TestTooltipRecallInvalid)
+    {
+        IndirectAddressTriggerViewModelHarness vmTrigger;
+        vmTrigger.mockGameContext.InitializeCodeNotes();
+        vmTrigger.Parse("A:{recall}_0xH0000=1");
+        vmTrigger.mockConfiguration.SetFeatureEnabled(ra::services::Feature::PreferDecimal, true);
+
+        const auto* pCondition1 = vmTrigger.Conditions().GetItemAt(0);
+        Expects(pCondition1 != nullptr);
+
+        // there is no Remember condition to point to
+        Assert::AreEqual(std::wstring(L"0x00000000 (recall)\r\n[invalid recall]"), pCondition1->GetTooltip(TriggerConditionViewModel::SourceTypeProperty));
+    }
+
+    TEST_METHOD(TestTooltipRecallInvalidInPauseIf)
+    {
+        IndirectAddressTriggerViewModelHarness vmTrigger;
+        vmTrigger.mockGameContext.InitializeCodeNotes();
+        vmTrigger.Parse("K:0xH0001*2_1=1_N:{recall}!=0_P:0xH0000=1");
+        vmTrigger.mockConfiguration.SetFeatureEnabled(ra::services::Feature::PreferDecimal, true);
+
+        const auto* pCondition3 = vmTrigger.Conditions().GetItemAt(2);
+        Expects(pCondition3 != nullptr);
+
+        // there is a Remember condition to point to, but it won't be processed until after this condition
+        Assert::AreEqual(std::wstring(L"0x00000000 (recall)\r\n[invalid recall]"), pCondition3->GetTooltip(TriggerConditionViewModel::SourceTypeProperty));
+    }
+
     TEST_METHOD(TestIsModifying)
     {
         TriggerConditionViewModelHarness condition;