[Memprof] Fixes memory leak in MemInfoBlock histogram. (llvm#96834)

MemInfoBlocks (MIB) with empty callstacks are erased prematurely from
the CallStackProfileData. This patch frees allocated histogram buffers
when the MIB is associated with an empty callstack.

Author: mattweingarten

llvm/lib/ProfileData/MemProfReader.cpp

@@ -633,6 +633,8 @@ Error RawMemProfReader::symbolizeAndFilterStackFrames(
   // Drop the entries where the callstack is empty.
   for (const uint64_t Id : EntriesToErase) {
     StackMap.erase(Id);
+    if(CallstackProfileData[Id].AccessHistogramSize > 0)
+      free((void*) CallstackProfileData[Id].AccessHistogram);
     CallstackProfileData.erase(Id);
   }