Make sure s_currentGenerationTable is safe for profiler attach (#78937)

Co-authored-by: Andrew Au <andrewau@microsoft.com>

src/coreclr/vm/proftoeeinterfaceimpl.cpp

@@ -901,7 +901,7 @@ void GenerationTable::Refresh()
 
 // This is the table of generation bounds updated by the gc
 // and read by the profiler.
-static GenerationTable *s_currentGenerationTable;
+static GenerationTable *s_currentGenerationTable = nullptr;
 
 // This is just so we can assert there's a single writer
 #ifdef  ENABLE_CONTRACTS
@@ -931,7 +931,6 @@ void __stdcall UpdateGenerationBounds()
     // Notify the profiler of start of the collection
     if (CORProfilerTrackGC() || CORProfilerTrackBasicGC())
     {
-
         if (s_currentGenerationTable == nullptr)
         {
             EX_TRY
@@ -965,7 +964,10 @@ void __stdcall ProfilerAddNewRegion(int generation, uint8_t* rangeStart, uint8_t
 #ifdef PROFILING_SUPPORTED
     if (CORProfilerTrackGC() || CORProfilerTrackBasicGC())
     {
-        s_currentGenerationTable->AddRecord(generation, rangeStart, rangeEnd, rangeEndReserved);
+        if (s_currentGenerationTable != nullptr)
+        {
+            s_currentGenerationTable->AddRecord(generation, rangeStart, rangeEnd, rangeEndReserved);
+        }
     }
 #endif // PROFILING_SUPPORTED
     RETURN;