Fix T1410

Summary:
Co-authored-by: Wilfrantz DEDE <contact@dede.dev>

We don't understand why there are two versions of many functions: `const type& at() const` and `type& at()`, for example.
`std::vector::at()` does the same thing. Why?

Test Plan: Build with `make ready` and confirm that it works in the use case in T1410.

Reviewers: ardunster

Reviewed By: ardunster

Subscribers: jcmcdonald, wdede, ardunster

Tags: #bss_team, #pawlib_project, #programming_dept

Differential Revision: https://phabricator.mousepawmedia.net/D362

pawlib-source/include/pawlib/base_flex_array.hpp

@@ -211,7 +211,12 @@ class Base_FlexArr
 
         const type& at(size_t index) const
         {
-            return at(index);
+            if(!validateIndex(index, false))
+            {
+                throw std::out_of_range("BaseFlexArray: Index out of range!");
+            }
+
+            return internalArray[toInternalIndex(index)];
         }
 
         /** Clear all the elements in the array.