Bug 1274444 - Check for null console before attempting to flash it; r=glandium

GetConsoleWindow() can return NULL. Previously, we may have passed a NULL
console reference into FlashWindowEx(). On my machine (when running in a
console), passing NULL doesn't seem to cause an error. But since we have
a report of this function hanging, it is quite possible it can cause
hangs in other scenarios. Since a NULL console won't result in any
notification, let's not call FlashWindowEx() when no console is available.

MozReview-Commit-ID: LrKX8weUkzX

--HG--
extra : rebase_source : 6c3fc724dbc038f6b51bbdc14d985202c47074e8

python/mozbuild/mozbuild/base.py

@@ -449,8 +449,15 @@ class MozbuildObject(ProcessExecutionMixin):
                 FLASHW_CAPTION = 0x01
                 FLASHW_TRAY = 0x02
                 FLASHW_TIMERNOFG = 0x0C
+
+                # GetConsoleWindows returns NULL if no console is attached. We
+                # can't flash nothing.
+                console = windll.kernel32.GetConsoleWindow()
+                if not console:
+                    return
+
                 params = FLASHWINDOW(sizeof(FLASHWINDOW),
-                                    windll.kernel32.GetConsoleWindow(),
+                                    console,
                                     FLASHW_CAPTION | FLASHW_TRAY | FLASHW_TIMERNOFG, 3, 0)
                 FlashWindowEx(params)
         except Exception as e: