Gmt module: Simplify code.

modules/gmt/modgmt_strcomp.h

@@ -76,7 +76,7 @@ class TemplateComparator
    switch(b->type)
    {
     case(Block::TEXT): {res+=s.substr(b->b,b->e-b->b); break;}
-    case(Block::OPTIONAL): {b=b->child.get(); goto next;}
+    case(Block::OPTIONAL):
     case(Block::VARIANTS): {b=b->child.get(); goto next;}
     case(Block::DELIM): {b=b->parent; break;}
     default: {}