Don't assert about missing profile info in createProfileWeightsForLoop

The compiler shouldn't crash if the profile info is slightly off. We hit
this in Chromium.

Differential revision: https://reviews.llvm.org/D79417

clang/lib/CodeGen/CodeGenPGO.cpp

@@ -1051,8 +1051,7 @@ llvm::MDNode *CodeGenFunction::createProfileWeightsForLoop(const Stmt *Cond,
   if (!PGO.haveRegionCounts())
     return nullptr;
   Optional<uint64_t> CondCount = PGO.getStmtCount(Cond);
-  assert(CondCount.hasValue() && "missing expected loop condition count");
-  if (*CondCount == 0)
+  if (!CondCount || *CondCount == 0)
     return nullptr;
   return createProfileWeights(LoopCount,
                               std::max(*CondCount, LoopCount) - LoopCount);