[omnibox] [entity-latency] Fix crashes on incotnito & guest profiles.

On creation (and ominbox changes), the omnibox attempts to wakeup the
current profile's BitmapFetcherService by invoking
BitmapFetcherService::WakeupDecoder. But incognito and guest profiles do
not have a BitmapFetcherService, resulting in calling WakeupDecoder on a
nullptr and crashing. The recent CL crrev.com/c/2348328 introduced this
wakeup call.

This CL adds a prior null check. Other usages of BitmapFetcherService
don't require a null check as they're conditioned on the existence of
omnibox images which requires a non-incognito/guest profile.

Bug: 1115108, 1128282
Change-Id: If0c21b6743182dfb7e5ab1d3f75fc7da6ee0bad1
Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/2411655
Commit-Queue: manuk hovanesian <manukh@chromium.org>
Reviewed-by: Tommy Li <tommycli@chromium.org>
Cr-Commit-Position: refs/heads/master@{#807134}

chrome/browser/ui/omnibox/chrome_omnibox_client.cc

@@ -472,8 +472,10 @@ void ChromeOmniboxClient::WakeupDecoder() {
           omnibox::kEntitySuggestionsReduceLatency,
           OmniboxFieldTrial::kEntitySuggestionsReduceLatencyDecoderWakeupParam,
           false)) {
-    BitmapFetcherServiceFactory::GetForBrowserContext(profile_)
-        ->WakeupDecoder();
+    if (auto* service =
+            BitmapFetcherServiceFactory::GetForBrowserContext(profile_)) {
+      service->WakeupDecoder();
+    }
   }
 }