[fix] engine - karmasearch crash when searching with long queries (#5912)

Karmasearch seem to crash when searching with long queries >= 100 characters.
The returned JSON is exactly this `["",[]]`, which will crash when trying to
access `resp.json()["results"]`

Close: https://github.com/searxng/searxng/issues/5911

Signed-off-by: Markus Heiser <markus.heiser@darmarit.de>

searx/engines/karmasearch.py

@@ -125,7 +125,11 @@ def _parse_images(result: dict[str, t.Any]) -> LegacyResult:
 def response(resp: "SXNG_Response") -> EngineResults:
     res = EngineResults()
 
-    for result in resp.json()["results"]:
+    json_resp: dict[str, t.Any] = resp.json()
+    if not isinstance(json_resp, dict):
+        return res  # pyright: ignore[reportUnreachable]
+
+    for result in json_resp["results"]:
         # hide sponsored results
         if result.get("sponsored", False):
             continue