Improved NULL checking in strreplace()

HISTORY

@@ -4201,3 +4201,4 @@ Video Disk Recorder Revision History
 - Fixed a crash after executing the SVDRP command CLRE, caused by dangling 'schedule'
   pointers from cChannel objects (reported by Malte Schröder).
 - Updated the Finnish OSD texts (thanks to Rolf Ahrenberg).
+- Improved NULL checking in strreplace().

tools.c

@@ -4,7 +4,7 @@
  * See the main source file 'vdr.c' for copyright information and
  * how to reach the author.
  *
- * $Id: tools.c 1.111 2006/01/15 16:42:37 kls Exp $
+ * $Id: tools.c 1.112 2006/01/20 14:01:28 kls Exp $
  */
 
 #include "tools.h"
@@ -138,13 +138,14 @@ char *strn0cpy(char *dest, const char *src, size_t n)
 
 char *strreplace(char *s, char c1, char c2)
 {
+  if (s) {
      char *p = s;
-
-  while (p && *p) {
+     while (*p) {
            if (*p == c1)
               *p = c2;
            p++;
            }
+     }
   return s;
 }