Bail out before allocating slides if file is empty

In load() we allocated slides before checking if we actually read
anything from the FILE fp and then continue with an allocated but
“empty” space wich would lead to errors.

sent.c

@@ -413,10 +413,6 @@ void load(FILE *fp)
 
 	/* read each line from fp and add it to the item list */
 	while (1) {
-		if ((slidecount+1) * sizeof(*slides) >= size)
-			if (!(slides = realloc(slides, (size += BUFSIZ))))
-				die("cannot realloc %u bytes:", size);
-
 		/* eat consecutive empty lines */
 		while ((p = fgets(buf, sizeof(buf), fp)))
 			if (strcmp(buf, "\n") != 0 && buf[0] != '#')
@@ -424,6 +420,10 @@ void load(FILE *fp)
 		if (!p)
 			break;
 
+		if ((slidecount+1) * sizeof(*slides) >= size)
+			if (!(slides = realloc(slides, (size += BUFSIZ))))
+				die("cannot realloc %u bytes:", size);
+
 		/* read one slide */
 		maxlines = 0;
 		memset((s = &slides[slidecount]), 0, sizeof(Slide));