classic: update Header.j2.tex for connections without urls

rendercv/themes/classic/Header.j2.tex

@@ -10,8 +10,14 @@
 
     \normalsize
     ((* for connection in cv.connections *))
-    \mbox{\hrefWithoutArrow{<<connection["url"]>>}{{\footnotesize<<connection["latex_icon"]>>}\hspace*{0.13cm}<<connection["placeholder"]>>}}
-    \hspace*{<<design.margins.header.horizontal_between_connections>>}
+    \mbox{
+        ((* if connection["url"] *))
+        \hrefWithoutArrow{<<connection["url"]>>}{{\footnotesize<<connection["latex_icon"]>>}\hspace*{0.13cm}<<connection["placeholder"]>>}
+        ((* else *))
+        {\footnotesize<<connection["latex_icon"]>>}\hspace*{0.13cm}<<connection["placeholder"]>>
+        ((* endif *))
+    }
+    \kern <<design.margins.header.horizontal_between_connections>>
     ((* endfor *))
 \end{header}