geanygendoc: Fix crash if trying to document an unknown type

Fix crash if the tag to generate documentation for is of an unknown
type.  Also consolidate some code around this to validate parameters
just to be more defensive in case it sill actually happens.

Fixes geany#1362.

geanygendoc/src/ggd-doc-type.c

@@ -128,9 +128,12 @@ ggd_doc_type_get_setting (const GgdDocType *doctype,
 {
   GgdDocSetting  *setting = NULL;
   GList          *tmp;
-  gssize          match_len = strlen (match);
+  gssize          match_len;
 
   g_return_val_if_fail (doctype != NULL, NULL);
+  g_return_val_if_fail (match != NULL, NULL);
+
+  match_len = (gssize) strlen (match);
 
   for (tmp = doctype->settings; tmp && ! setting; tmp = g_list_next (tmp)) {
     if (ggd_doc_setting_matches (tmp->data, match, match_len)) {
@@ -177,6 +180,7 @@ ggd_doc_type_resolve_setting (const GgdDocType  *doctype,
   gchar         *child_match = NULL;
 
   g_return_val_if_fail (doctype != NULL, NULL);
+  g_return_val_if_fail (match != NULL, NULL);
 
   /*g_debug ("Resolving match \"%s\"...", child_match);*/
   if (nth_child) (*nth_child) = 0;

geanygendoc/src/ggd.c

@@ -383,22 +383,25 @@ get_setting_from_tag (GgdDocType     *doctype,
                       const TMTag    *tag,
                       const TMTag   **real_tag)
 {
-  GgdDocSetting  *setting;
+  GgdDocSetting  *setting = NULL;
   gchar          *hierarchy;
-  gint            nth_child;
   GPtrArray      *tag_array = doc->tm_file->tags_array;
   GeanyFiletypeID geany_ft = FILETYPE_ID (doc->file_type);
 
   hierarchy = ggd_tag_resolve_type_hierarchy (tag_array, geany_ft, tag);
   /*g_debug ("type hierarchy for tag %s is: %s", tag->name, hierarchy);*/
-  setting = ggd_doc_type_resolve_setting (doctype, hierarchy, &nth_child);
   *real_tag = tag;
-  if (setting) {
-    for (; nth_child > 0; nth_child--) {
-      *real_tag = ggd_tag_find_parent (tag_array, geany_ft, *real_tag);
+  if (hierarchy) {
+    gint  nth_child;
+
+    setting = ggd_doc_type_resolve_setting (doctype, hierarchy, &nth_child);
+    if (setting) {
+      for (; nth_child > 0; nth_child--) {
+        *real_tag = ggd_tag_find_parent (tag_array, geany_ft, *real_tag);
+      }
     }
+    g_free (hierarchy);
   }
-  g_free (hierarchy);
 
   return setting;
 }