Replace uses of the isNull and isNonnull soy functions with comparisons with the null literal.

These functions were introduced in Soy v1 to solve a problem with the
expression parser. The language has since added support for more
idiomatic comparison patterns; migrate code to use them.

PiperOrigin-RevId: 379600497
Change-Id: I78e29703385ccba83a72942dfa1191f1c6516dad
diff --git a/resources/com/google/gitiles/templates/BlameDetail.soy b/resources/com/google/gitiles/templates/BlameDetail.soy
index e495093..366419d 100644
--- a/resources/com/google/gitiles/templates/BlameDetail.soy
+++ b/resources/com/google/gitiles/templates/BlameDetail.soy
@@ -51,7 +51,7 @@
       {let $i: index($line) /}
       {let $region: $regions[$i] /}
       <tr class="Blame-region {$region.class}">
-        {if isNonnull($region.abbrevSha)}
+        {if $region.abbrevSha != null}
           <td class="Blame-author">{$region.author.name}</td>
           <td class="Blame-sha1"><a class="u-sha1 u-monospace Blame-sha1" href="{$region.commitUrl}">{$region.abbrevSha}</a></td>
           <td class="Blame-time">{$region.author.time}</td>
diff --git a/resources/com/google/gitiles/templates/ObjectDetail.soy b/resources/com/google/gitiles/templates/ObjectDetail.soy
index ac5d98e..b4f4426 100644
--- a/resources/com/google/gitiles/templates/ObjectDetail.soy
+++ b/resources/com/google/gitiles/templates/ObjectDetail.soy
@@ -81,7 +81,7 @@
           <a href="{$parent.url}">{$parent.sha}</a>
           {sp}<span>
             [<a href="{$parent.diffUrl}">{msg desc="text for the parent diff link"}diff{/msg}</a>]
-            {if isNonnull($parent.blameUrl)}
+            {if $parent.blameUrl != null}
               {sp}[<a href="{$parent.blameUrl}">{msg desc="text for the parent blame link"}blame{/msg}</a>]
             {/if}
           </span>