tool_urlglob.c: Fixed compiler warnings

warning: 'variable' may be used uninitialized in this function
diff --git a/src/tool_urlglob.c b/src/tool_urlglob.c
index ac13d68..1644077 100644
--- a/src/tool_urlglob.c
+++ b/src/tool_urlglob.c
@@ -249,8 +249,8 @@
   else if(ISDIGIT(*pattern)) {
     /* numeric range detected */
     unsigned long min_n;
-    unsigned long max_n;
-    unsigned long step_n;
+    unsigned long max_n = 0;
+    unsigned long step_n = 0;
     char *endp;
 
     pat->type = UPTNumRange;