Repro case with a master build: https://codesandbox.io/s/stoic-mcnulty-dhygf?file=/src/App.js:668-703

Expected: we see content after a second.
Actual: fallback never resolves.

This happens in a sequence of:

1. Normal update
   - which suspends
2. Idle update
   - which also suspends
3. An unrelated normal update immediately followed by a ping (so they're batched)
   - here, we decide to stay on fallback, but should've shown the content

If you remove `_setVersion(v => v + 1);` on line 44 then the issue goes away.
if (progressedPrimaryChild !== currentPrimaryChildFragment.child) {
            primaryChildFragment.child = progressedPrimaryChild;
            let progressedChild = progressedPrimaryChild;
            while (progressedChild !== null) {
              progressedChild.return = primaryChildFragment;
              progressedChild = progressedChild.sibling;
            }
          }
        }
         
         
        if (enableProfilerTimer && workInProgress.mode & ProfileMode) {
           
          let treeBaseDuration = 0;
          let hiddenChild = primaryChildFragment.child;
          while (hiddenChild !== null) {
            treeBaseDuration += hiddenChild.treeBaseDuration;
            hiddenChild = hiddenChild.sibling;
          }
          primaryChildFragment.treeBaseDuration = treeBaseDuration;
        }
         
         
        const fallbackChildFragment = createWorkInProgress(
          currentFallbackChildFragment,
          nextFallbackChildren,
        );
        fallbackChildFragment.return = workInProgress;
        primaryChildFragment.sibling = fallbackChildFragment;
        primaryChildFragment.childExpirationTime = getRemainingWorkInPrimaryTree(