Revert "[App] add a missing return statement (#6519)"

This reverts commit 5c7ef17ac063f9339c68333afecf1cd88404b959.

src/App/AutoTransaction.h

@@ -31,9 +31,7 @@ class Application;
 class AppExport AutoTransaction {
 private:
     /// Private new operator to prevent heap allocation
-    void* operator new(size_t size) {
-        return nullptr;
-    };
+    void* operator new(size_t size);
 
 public:
     /** Constructor
@@ -122,9 +120,7 @@ public:
 
 private:
     /// Private new operator to prevent heap allocation
-    void* operator new(size_t size) {
-        return nullptr;
-    };
+    void* operator new(size_t size);
 
 private:
     bool active;