[clang][dataflow] Remove buggy assertion. (#67311)

The assertion fails on the test
TransferTest.EvaluateBlockWithUnreachablePreds
(which I think, ironically, was introuced in the same patch as the
assertion).

This just wasn't obvious because the assertion is inside an `LLVM_DEBUG`
block
and is thus only executed if the command-line flag `-debug` is passed.
We don't
have any CI builds that do this, so it's almost guaranteed that
assertions like
this will start failing over time (if they ever passed in the first
place --
which I'm not sure about here).

It's not clear to me whether there's _some_ assertion we might be able
to make
here -- I've looked at this for a while but haven't been able to come up
with
anything obvious. For the time being, I think it's best to simply delete
the
assertion.

Author: martinboehme

clang/lib/Analysis/FlowSensitive/Transfer.cpp

@@ -43,20 +43,8 @@ const Environment *StmtToEnvMap::getEnvironment(const Stmt &S) const {
   if (!CFCtx.isBlockReachable(*BlockIt->getSecond()))
     return nullptr;
   const auto &State = BlockToState[BlockIt->getSecond()->getBlockID()];
-  if (!(State)) {
-    LLVM_DEBUG({
-      // State can be null when this block is unreachable from the block that
-      // called this method.
-      bool hasUnreachableEdgeFromPred = false;
-      for (auto B : BlockIt->getSecond()->preds())
-        if (!B) {
-          hasUnreachableEdgeFromPred = true;
-          break;
-        }
-      assert(hasUnreachableEdgeFromPred);
-    });
+  if (!(State))
     return nullptr;
-  }
   return &State->Env;
 }