LaTeX template: don't emit empty linkcolor= in hypersetup.

Closes #11098.

data/templates/default.latex

@@ -95,7 +95,9 @@ $if(toc-title)$
 $endif$
 {
 $if(colorlinks)$
-\hypersetup{linkcolor=$if(toccolor)$$toccolor$$else$$endif$}
+$if(toccolor)$
+\hypersetup{linkcolor=$toccolor$}
+$endif$
 $endif$
 \setcounter{tocdepth}{$toc-depth$}
 \tableofcontents