Bug 1644009 - P14. Fallback to normal dispatch on release. r=bholley

We shouldn't ever get there, but just in case, better than a null deref.

Differential Revision: https://phabricator.services.mozilla.com/D79097

xpcom/threads/MozPromise.h

@@ -478,7 +478,10 @@ class MozPromise : public MozPromiseBase {
             this);
         nsCOMPtr<nsIDirectTaskDispatcher> dispatcher =
             do_QueryInterface(mResponseTarget);
-        if (!dispatcher) {
+        if (dispatcher) {
+          dispatcher->DispatchDirectTask(r.forget());
+          return;
+        }
         NS_WARNING(
             nsPrintfCString(
                 "Direct Task dispatching not available for thread \"%s\"",
@@ -486,11 +489,8 @@ class MozPromise : public MozPromiseBase {
                 .get());
         MOZ_DIAGNOSTIC_ASSERT(
             false,
-              "mResponseTarget must implement nsIDirectTaskDispatcher for "
-              "direct task dispatching");
-        }
-        dispatcher->DispatchDirectTask(r.forget());
-        return;
+            "mResponseTarget must implement nsIDirectTaskDispatcher for direct "
+            "task dispatching");
       }
 
       // Promise consumers are allowed to disconnect the Request object and