diff --git a/application/palemoon/app/blocklist.xml b/application/palemoon/app/blocklist.xml
index fa594aabea..2b88db9545 100644
--- a/application/palemoon/app/blocklist.xml
+++ b/application/palemoon/app/blocklist.xml
@@ -1,5 +1,5 @@
 <?xml version='1.0' encoding='utf-8'?>
-<blocklist lastupdate="1554898538000"
+<blocklist lastupdate="1612384668000"
 xmlns="http://www.mozilla.org/2006/addons-blocklist">
   <emItems>
     <emItem blockID="i545" id="superlrcs@svenyor.net">
@@ -2529,6 +2529,10 @@ xmlns="http://www.mozilla.org/2006/addons-blocklist">
       </versionRange>
       <prefs></prefs>
     </emItem>
+    <emItem blockID="pm117" id="treestyletabforpm@oinkoink">
+      <versionRange minVersion="0" maxVersion="0.0.5" severity="3">
+      </versionRange>
+    <emItem>
   </emItems>
   <pluginItems>
     <pluginItem blockID="p26">
diff --git a/application/palemoon/branding/shared/pref/uaoverrides.inc b/application/palemoon/branding/shared/pref/uaoverrides.inc
index fc086d662f..a5307879f2 100644
--- a/application/palemoon/branding/shared/pref/uaoverrides.inc
+++ b/application/palemoon/branding/shared/pref/uaoverrides.inc
@@ -34,9 +34,6 @@ pref("@GUAO_PREF@.outlook.com","Mozilla/5.0 (%OS_SLICE% rv:@GK_VERSION@) @GK_SLI
 pref("@GUAO_PREF@.web.de","Mozilla/5.0 (%OS_SLICE% rv:@GK_VERSION@) @GK_SLICE@ @FX_SLICE@ (Pale Moon)");
 pref("@GUAO_PREF@.yahoo.com","Mozilla/5.0 (%OS_SLICE% rv:99.9) @GK_SLICE@ Firefox/99.9");
 pref("@GUAO_PREF@.calendar.yahoo.com","Mozilla/5.0 (%OS_SLICE% rv:@GK_VERSION@) @GK_SLICE@ @FX_SLICE@ (Pale Moon)");
-pref("@GUAO_PREF@.youtube.com","Mozilla/5.0 (%OS_SLICE% rv:60.0) @GK_SLICE@ Firefox/60.0");
-pref("@GUAO_PREF@.studio.youtube.com","Mozilla/5.0 (%OS_SLICE% rv:71.0) @GK_SLICE@ Firefox/71.0");
-pref("@GUAO_PREF@.gaming.youtube.com","Mozilla/5.0 (%OS_SLICE% rv:71.0) @GK_SLICE@ Firefox/71.0");
 
 // For Amazon Prime videos
 pref("@GUAO_PREF@.www.amazon.com","Mozilla/5.0 (%OS_SLICE% rv:45.9) @GK_SLICE@ Firefox/45.9 (Pale Moon)");
@@ -65,6 +62,9 @@ pref("@GUAO_PREF@.netflximg.net","Mozilla/5.0 (Windows NT 6.1; rv:45.9) @GK_SLIC
 
 // UA-sniffing domains that are "app/vendor-specific" and do not like Pale Moon
 pref("@GUAO_PREF@.web.whatsapp.com","Mozilla/5.0 (Windows NT 10.0; Win64; x64) AppleWebKit/537.36 (KHTML, like Gecko) Chrome/70.0.3538.77 Safari/537.36");
+pref("@GUAO_PREF@.youtube.com","Mozilla/5.0 (%OS_SLICE% rv:60.0) @GK_SLICE@ Firefox/60.0");
+pref("@GUAO_PREF@.studio.youtube.com","Mozilla/5.0 (%OS_SLICE% rv:68.0) @GK_SLICE@ @GRE_VERSION_SLICE@ Firefox/68.0 @PM_SLICE@");
+pref("@GUAO_PREF@.gaming.youtube.com","Mozilla/5.0 (%OS_SLICE% rv:71.0) @GK_SLICE@ Firefox/71.0");
 
 // The following domains do not like the Goanna slice
 pref("@GUAO_PREF@.hitbox.tv","Mozilla/5.0 (%OS_SLICE% rv:@GK_VERSION@) @GK_SLICE@ @FX_SLICE@");
diff --git a/layout/base/nsCSSFrameConstructor.cpp b/layout/base/nsCSSFrameConstructor.cpp
index 2cc5ec818d..b40e6f8b61 100644
--- a/layout/base/nsCSSFrameConstructor.cpp
+++ b/layout/base/nsCSSFrameConstructor.cpp
@@ -6464,6 +6464,11 @@ nsCSSFrameConstructor::IsValidSibling(nsIFrame*              aSibling,
                                       nsIContent*            aContent,
                                       StyleDisplay&          aDisplay)
 {
+  if (!aSibling || !aContent) {
+    // If either of these are null, no sane comparison can be made.
+    return false;
+  }
+  
   nsIFrame* parentFrame = aSibling->GetParent();
   nsIAtom* parentType = parentFrame->GetType();