ccmake: Fix crash when deleting all cache entries

Prevents crash when deleting all cache entries.
Additionally, if advanced entries are hidden, no longer show the first advanced
entry when deleting all visible entries.

Fixes: #23499

Source/CursesDialog/cmCursesMainForm.cxx

@@ -93,13 +93,13 @@ void cmCursesMainForm::InitializeUI()
 
   int entrywidth = this->InitialWidth - 35;
 
-  if (count == 0) {
-    // If cache is empty, display a label saying so and a
-    // dummy entry widget (does not respond to input)
-    cmCursesCacheEntryComposite comp("EMPTY CACHE", 30, 30);
-    comp.Entry = cm::make_unique<cmCursesDummyWidget>(1, 1, 1, 1);
-    newEntries.emplace_back(std::move(comp));
-  } else {
+  // Add a label to display when cache is empty
+  // dummy entry widget (does not respond to input)
+  cmCursesCacheEntryComposite comp("EMPTY CACHE", 30, 30);
+  comp.Entry = cm::make_unique<cmCursesDummyWidget>(1, 1, 1, 1);
+  newEntries.emplace_back(std::move(comp));
+
+  if (count > 0) {
     // Create the composites.
 
     // First add entries which are new
@@ -190,7 +190,8 @@ void cmCursesMainForm::RePost()
     this->Fields.push_back(entry.Entry->Field);
   }
   // if no cache entries there should still be one dummy field
-  if (this->Fields.empty()) {
+  this->IsEmpty = this->Fields.empty();
+  if (this->IsEmpty) {
     const auto& front = this->Entries.front();
     this->Fields.push_back(front.Label->Field);
     this->Fields.push_back(front.IsNewLabel->Field);
@@ -869,7 +870,7 @@ void cmCursesMainForm::HandleInput()
         }
       }
       // delete cache entry
-      else if (key == 'd' && this->NumberOfVisibleEntries) {
+      else if (key == 'd' && this->NumberOfVisibleEntries && !this->IsEmpty) {
         this->OkToGenerate = false;
         FIELD* cur = current_field(this->Form);
         size_t findex = field_index(cur);

Source/CursesDialog/cmCursesMainForm.h

@@ -161,6 +161,7 @@ protected:
   bool OkToGenerate = false;
   // Number of pages displayed
   int NumberOfPages = 0;
+  bool IsEmpty = false;
 
   int InitialWidth;
   std::unique_ptr<cmake> CMakeInstance;