Prevent NPE when viewing non-rendered files (#18234)

Fix #18231

Signed-off-by: Andrew Thornton <art27@cantab.net>

templates/repo/unicode_escape_prompt.tmpl

@@ -1,17 +1,19 @@
-{{if .EscapeStatus.BadBIDI}}
-<div class="ui error message unicode-escape-prompt">
+{{if .EscapeStatus}}
+	{{if .EscapeStatus.BadBIDI}}
+		<div class="ui error message unicode-escape-prompt">
 			<span class="close icon hide-panel button" data-panel-closest=".message">{{svg "octicon-x" 16 "close inside"}}</span>
 			<div class="header">
 				{{$.root.i18n.Tr "repo.bidi_bad_header"}}
 			</div>
 			<p>{{$.root.i18n.Tr "repo.bidi_bad_description" | Str2html}}</p>
-</div>
-{{else if .EscapeStatus.Escaped}}
-<div class="ui warning message unicode-escape-prompt">
+		</div>
+	{{else if .EscapeStatus.Escaped}}
+		<div class="ui warning message unicode-escape-prompt">
 			<span class="close icon hide-panel button" data-panel-closest=".message">{{svg "octicon-x" 16 "close inside"}}</span>
 			<div class="header">
 				{{$.root.i18n.Tr "repo.unicode_header"}}
 			</div>
 			<p>{{$.root.i18n.Tr "repo.unicode_description" | Str2html}}</p>
-</div>
+		</div>
+	{{end}}
 {{end}}