Bug 1605514 - Avoid hard-crashing on malformed data while fuzzing, r=mccr8

Differential Revision: https://phabricator.services.mozilla.com/D58986

--HG--
extra : moz-landing-system : lando

docshell/base/BrowsingContext.cpp

@@ -1502,6 +1502,7 @@ bool IPDLParamTraits<dom::BrowsingContext*>::Read(
 
   RefPtr<dom::BrowsingContext> browsingContext = dom::BrowsingContext::Get(id);
   if (!browsingContext) {
+#ifndef FUZZING
     // NOTE: We could fail softly by returning `false` if the `BrowsingContext`
     // isn't present, but doing so will cause a crash anyway. Let's improve
     // diagnostics by reliably crashing here.
@@ -1509,6 +1510,7 @@ bool IPDLParamTraits<dom::BrowsingContext*>::Read(
     // If we can recover from failures to deserialize in the future, this crash
     // should be removed or modified.
     MOZ_CRASH("Attempt to deserialize absent BrowsingContext");
+#endif
     *aResult = nullptr;
     return false;
   }