Fix dismissed error overlays

Author: deftomat

packages/react-dev-utils/webpackHotDevClient.js

@@ -106,7 +106,7 @@ function handleSuccess() {
     tryApplyUpdates(function onHotUpdateSuccess() {
       // Only dismiss it when we're sure it's a hot update.
       // Otherwise it would flicker right before the reload.
-      ErrorOverlay.dismissBuildError();
+      tryDismissErrorOverlay();
     });
   }
 }
@@ -147,7 +147,7 @@ function handleWarnings(warnings) {
     tryApplyUpdates(function onSuccessfulHotUpdate() {
       // Only dismiss it when we're sure it's a hot update.
       // Otherwise it would flicker right before the reload.
-      ErrorOverlay.dismissBuildError();
+      tryDismissErrorOverlay();
     });
   }
 }
@@ -179,6 +179,12 @@ function handleErrors(errors) {
   // We will reload on next success instead.
 }
 
+function tryDismissErrorOverlay() {
+  if (!hasCompileErrors) {
+    ErrorOverlay.dismissBuildError();
+  }
+}
+
 // There is a newer version of the code available.
 function handleAvailableHash(hash) {
   // Update last known compilation hash.