Fix for infinite loop in cycle_competions, and potential issue in

fish_pager when given an empty completion list

fish_pager.cpp

@@ -1370,6 +1370,11 @@ int main(int argc, char **argv)
 
 //    debug( 3, L"prefix is '%ls'", prefix );
 
+    if (comp.empty())
+    {
+        exit_without_destructors(EXIT_FAILURE);
+    }
+
     init(mangle_descriptors, result_fd);
 
     mangle_descriptions(comp);

reader.cpp

@@ -1702,18 +1702,17 @@ static const completion_t *cycle_competions(const std::vector<completion_t> &com
     if (size == 0)
         return NULL;
 
+    // note start_idx will be set to -1 initially, so that when it gets incremented we start at 0
     const size_t start_idx = *inout_idx;
     size_t idx = start_idx;
+    
     const completion_t *result = NULL;
-    for (;;)
+    size_t remaining = comp.size();
+    while (remaining--)
     {
         /* Bump the index */
         idx = (idx + 1) % size;
 
-        /* Bail if we've looped */
-        if (idx == start_idx)
-            break;
-
         /* Get the completion */
         const completion_t &c = comp.at(idx);