stabilize text widget when no string is available; info message when serdisplib cannot open port

git-svn-id: https://ssl.bulix.org/svn/lcd4linux/trunk@1192 3ae390bd-cb1e-0410-b409-cd5a39f66f1f

drv_serdisplib.c

@@ -164,6 +164,7 @@ static int drv_SD_start(const char *section)
     sdcd = SDCONN_open(port);
     if (sdcd == NULL) {
 	error("%s: open(%s) failed: %s", Name, port, sd_geterrormsg());
+        info("%s: examples:\n  serraw:/dev/ttyS0\n  par:/dev/parport0\n  USB:<vendor>/<product>", Name);
 	return -1;
     }
 

svn_version.h

@@ -1 +1 @@
-#define SVN_VERSION "1158"
+#define SVN_VERSION "1192"

widget_text.c

@@ -58,6 +58,10 @@
 void widget_text_scroll(void *Self)
 {
     WIDGET *W = (WIDGET *) Self;
+    if (NULL == W || NULL == W->data) {
+        error("Warning: internal data error in Textwidget");
+        return;
+    }
     WIDGET_TEXT *T = W->data;
 
     char *prefix = P2S(&T->prefix);
@@ -68,6 +72,10 @@ void widget_text_scroll(void *Self)
     int num, len, width, pad;
     char *src, *dst;
 
+    if (NULL == string) {
+        error("Warning: Widget %s has no string", W->name);
+        return;
+    }
     num = 0;
     len = strlen(string);
     width = T->width - strlen(prefix) - strlen(postfix);