added NULL check to webserver.c

src/webserver.c

@@ -18,12 +18,25 @@ static char post_buffer[400];
 static uint16_t post_buffer_len = 0;
 
 void parse_post(const char *key, char delimiter, char *dest, int max_len) {
-  char *pos = strstr(post_buffer, key) + strlen(key);
-  char *end = strchr(pos, delimiter);
+  char *start = strstr(post_buffer, key);
+  if (!start) {
+    dest[0] = '\0';
+    return;
+  }
+
+  char *pos = start + strlen(key);
+  char *end = (delimiter == '\0') ? (post_buffer + strlen(post_buffer))
+                                  : strchr(pos, delimiter);
+
+  if (!end) {
+    end = post_buffer + strlen(post_buffer);
+  }
+
   int len = end - pos;
   if (len > max_len) {
     len = max_len;
   }
+
   strncpy(dest, pos, len);
   dest[len] = '\0';
 }