xrdp_orders_rail: fix g_mbstowcs error handling

libxrdp/xrdp_orders_rail.c

@@ -267,7 +267,11 @@ xrdp_orders_send_window_new_update(struct xrdp_orders *self, int window_id,
         /* titleInfo */
         num_chars = g_mbstowcs(0, window_state->title_info, 0);
         num_chars = MIN(num_chars, sizeof(twchar) * (g_strlen(window_state->title_info) + 1));
-        num_chars = MAX(num_chars, 0);
+        if (num_chars < 0)
+        {
+            /* g_mbstowcs failed, ignore text */
+            num_chars = 0;
+        }
         order_size += 2 * num_chars + 2;
     }
 
@@ -545,7 +549,11 @@ xrdp_orders_send_notify_new_update(struct xrdp_orders *self,
         /* ToolTip (variable) UNICODE_STRING */
         num_chars = g_mbstowcs(0, notify_state->tool_tip, 0);
         num_chars = MIN(num_chars, sizeof(twchar) * (g_strlen(notify_state->tool_tip) + 1));
-        num_chars = MAX(num_chars, 0);
+        if (num_chars < 0)
+        {
+            /* g_mbstowcs failed, ignore text */
+            num_chars = 0;
+        }
         order_size += 2 * num_chars + 2;
     }
 
@@ -555,12 +563,20 @@ xrdp_orders_send_notify_new_update(struct xrdp_orders *self,
         /* UNICODE_STRING */
         num_chars = g_mbstowcs(0, notify_state->infotip.title, 0);
         num_chars = MIN(num_chars, sizeof(twchar) * (g_strlen(notify_state->infotip.title) + 1));
-        num_chars = MAX(num_chars, 0);
+        if (num_chars < 0)
+        {
+            /* g_mbstowcs failed, ignore text */
+            num_chars = 0;
+        }
         order_size += 2 * num_chars + 2;
         /* UNICODE_STRING */
         num_chars = g_mbstowcs(0, notify_state->infotip.text, 0);
         num_chars = MIN(num_chars, sizeof(twchar) * (g_strlen(notify_state->infotip.text) + 1));
-        num_chars = MAX(num_chars, 0);
+        if (num_chars < 0)
+        {
+            /* g_mbstowcs failed, ignore text */
+            num_chars = 0;
+        }
         order_size += 2 * num_chars + 2;
         /* Timeout (4 bytes) */
         /* InfoFlags (4 bytes) */