Handle unexpected values for character passed to isalnum

It seems that certain negative integer values can crash isalnum().
Let's protect against those.

Fixes #711.

1 files changed, 1 insertions, 1 deletions

diff --git a/Panel.c b/Panel.c
index 8c4d44fc..1e53b4a4 100644
--- a/Panel.c
+++ b/Panel.c
@@ -469,7 +469,7 @@ HandlerResult Panel_selectByTyping(Panel* this, int ch) {
       this->eventHandlerState = xCalloc(100, sizeof(char));
    char* buffer = this->eventHandlerState;
 
-   if (ch < 255 && isalnum(ch)) {
+   if (ch > 0 && ch < 255 && isalnum(ch)) {
       int len = strlen(buffer);
       if (len < 99) {
          buffer[len] = ch;