Try to fix issues reported by coverity

src/apps/httpd/httpd.c

@@ -1728,7 +1728,11 @@ http_post_rxpbuf(struct http_state *hs, struct pbuf *p)
   /* prevent connection being closed if httpd_post_data_recved() is called nested */
   hs->unrecved_bytes++;
 #endif
-  err = httpd_post_receive_data(hs, p);
+  if (p != NULL) {
+    err = httpd_post_receive_data(hs, p);
+  } else {
+    err = ERR_OK;
+  }
 #if LWIP_HTTPD_SUPPORT_POST && LWIP_HTTPD_POST_MANUAL_WND
   hs->unrecved_bytes--;
 #endif

src/apps/httpd/makefsdata/makefsdata.c

@@ -763,6 +763,7 @@ static int checkSsiByFilelist(const char* filename_listfile)
     fclose(f);
     if ((readcount > fsize) || !readcount) {
       printf("failed to read data from ssi file\n");
+      free(buf);
       return 0;
     }
 
@@ -780,6 +781,7 @@ static int checkSsiByFilelist(const char* filename_listfile)
     lines = (char**)malloc(sizeof(char*) * num_lines);
     if (!lines) {
       printf("failed to allocate ssi line buffer\n");
+      free(buf);
       return 0;
     }
     memset(lines, 0, sizeof(char*) * num_lines);