Treat empty line input as "no input"

Do not insert a "newline" token if user inputs empty line. This let's
user to continue the output after she has been asked by reverse prompt
for more data. Otherwise an empty-line input would insert a "newline"
token which would break the flow of the conversation.

examples/main/main.cpp

@@ -465,6 +465,10 @@ int main(int argc, char ** argv) {
                 // done taking input, reset color
                 set_console_state(CONSOLE_STATE_DEFAULT);
 
+                // Add tokens to buffer only if the line is non-empty.
+                // This let's the user make the chat continue if it was stopped
+                // on a reverse prompt.
+                if (buffer.length() > 1) {
                     auto line_inp = ::llama_tokenize(ctx, buffer, false);
                     embd_inp.insert(embd_inp.end(), line_inp.begin(), line_inp.end());
 
@@ -473,6 +477,7 @@ int main(int argc, char ** argv) {
                     }
 
                     n_remain -= line_inp.size();
+		}
 
                 input_noecho = true; // do not echo this again
             }