[rule34us:tag] support URLs with empty 'q' query parameter (#8546)

gallery_dl/extractor/rule34us.py

@@ -57,7 +57,7 @@ class Rule34usTagExtractor(Rule34usExtractor):
     subcategory = "tag"
     directory_fmt = ("{category}", "{search_tags}")
     archive_fmt = "t_{search_tags}_{id}"
-    pattern = r"(?:https?://)?rule34\.us/index\.php\?r=posts/index&q=([^&#]+)"
+    pattern = r"(?:https?://)?rule34\.us/index\.php\?r=posts/index&q=([^&#]*)"
     example = "https://rule34.us/index.php?r=posts/index&q=TAG"
 
     def __init__(self, match):

test/results/rule34us.py

@@ -14,6 +14,15 @@ __tests__ = (
     "#class"   : rule34us.Rule34usTagExtractor,
     "#pattern" : r"https://img\d*\.rule34\.us/images/../../[0-9a-f]{32}\.\w+",
     "#count"   : 10,
+
+    "search_tags": "[terios]_elysion",
+},
+
+{
+    "#url"     : "https://rule34.us/index.php?r=posts/index&q=",
+    "#comment" : "empty 'q' query parameter (#8546)",
+    "#category": ("booru", "rule34us", "tag"),
+    "#class"   : rule34us.Rule34usTagExtractor,
 },
 
 {