fix cppchecker - null checks

client/src/proxmark3.c

@@ -519,6 +519,10 @@ static void set_my_user_directory(void) {
 
         uint16_t pathLen = FILENAME_MAX; // should be a good starting point
         char *cwd_buffer = (char *)calloc(pathLen, sizeof(uint8_t));
+        if (cwd_buffer == NULL) {
+            PrintAndLogEx(WARNING, "failed to allocate memory");
+            return;            
+        }
 
         while (GetCurrentDir(cwd_buffer, pathLen) == NULL) {
             if (errno == ERANGE) {  // Need bigger buffer

client/src/scripting.c

@@ -1279,10 +1279,12 @@ static int l_ewd(lua_State *L) {
 static int l_cwd(lua_State *L) {
 
     uint16_t path_len = FILENAME_MAX; // should be a good starting point
-    bool error = false;
     char *cwd = (char *)calloc(path_len, sizeof(uint8_t));
+    if (cwd == NULL) {
+        return returnToLuaWithError(L, "Failed to allocate memory");        
+    }
 
-    while (!error && (GetCurrentDir(cwd, path_len) == NULL)) {
+    while (GetCurrentDir(cwd, path_len) == NULL) {
         if (errno == ERANGE) {  // Need bigger buffer
             path_len += 10;      // if buffer was too small add 10 characters and try again
             cwd = realloc(cwd, path_len);