- fat32: returning -1 on file open failure

fs/fat32/fat32.c

@@ -520,9 +520,21 @@ uint32_t fat32_read_file_random_access(const Fat32_CtrlBlock *ctrl, const Fat32_
 
 // -----------------
 
+/**
+ * Open file.
+ * 
+ * @param ctrl pointer to FAT32 control block
+ * @param path full file path
+ * @param file_helper pointer to file helper object
+ * @return int 0 if successful, -1 on failure
+ */
 int fat32_open_file(const Fat32_CtrlBlock *ctrl, const char *path, Fat32_FileHelper *file_helper) {
     uint32_t file_entry_ba;
     const Fat32_FileEntry *entry = fat32_locate_file(ctrl, path, &file_entry_ba);
+    if (entry == NULL) { // if cannot open file, then return -1
+        return -1;
+    }
+
     uint32_t first_cluster = fat32_get_first_cluster(entry);
 
     // store data usable for identifying file on the storage