Check for an existing SVGResourceClient before invalidating filter

In some fairly generic code-paths we can have a 'filter' property while
not actually applying it - and thus don't have a SVGResourceClient.
(For example for 'filter' on <feImage>.)

Bug: 1158392, 1028063
Change-Id: I12bf8b6120a17f750582f037d59951a565731210
Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/2589837
Auto-Submit: Fredrik Söderquist <fs@opera.com>
Commit-Queue: Stephen Chenney <schenney@chromium.org>
Reviewed-by: Stephen Chenney <schenney@chromium.org>
Cr-Commit-Position: refs/heads/master@{#836776}

third_party/blink/renderer/core/layout/svg/svg_resources.cc

@@ -352,8 +352,10 @@ SVGResourceInvalidator::SVGResourceInvalidator(LayoutObject& object)
 
 void SVGResourceInvalidator::InvalidateEffects() {
   const ComputedStyle& style = object_.StyleRef();
-  if (style.HasFilter() && style.Filter().HasReferenceFilter())
-    SVGResources::GetClient(object_)->InvalidateFilterData();
+  if (style.HasFilter() && style.Filter().HasReferenceFilter()) {
+    if (SVGElementResourceClient* client = SVGResources::GetClient(object_))
+      client->InvalidateFilterData();
+  }
   if (style.ClipPath()) {
     object_.SetShouldDoFullPaintInvalidation();
     object_.InvalidateClipPathCache();