#3967: Correct a crash in count() and find() methods of string-like objects.
For example:
   "".count("xxxx", sys.maxint, 0)

Backport of r66631.
diff --git a/Objects/stringlib/find.h b/Objects/stringlib/find.h
index 4cdbb09..ffb9e36 100644
--- a/Objects/stringlib/find.h
+++ b/Objects/stringlib/find.h
@@ -14,11 +14,10 @@
 {
     Py_ssize_t pos;
 
-    if (sub_len == 0) {
-        if (str_len < 0)
-            return -1;
+    if (str_len < 0)
+        return -1;
+    if (sub_len == 0)
         return offset;
-    }
 
     pos = fastsearch(str, str_len, sub, sub_len, FAST_SEARCH);