X11: check crtcInfo for NULL when polling monitors

CONTRIBUTORS.md

@@ -287,6 +287,7 @@ video tutorials.
  - Xo Wang
  - Andre Weissflog
  - Jay Weisskopf
+ - Drew Weymouth
  - Frank Wille
  - Andy Williams
  - Joel Winarske

README.md

@@ -145,6 +145,7 @@ information on what to include when reporting a bug.
  - [Wayland] Bugfix: The cursor position was not updated when clicking through
    from a modal to the content area
  - [X11] Bugfix: Running without a WM could trigger an assert (#2593,#2601,#2631)
+ - [X11] Bugfix: Occasional crash when an idle display awakes (#2766) 
  - [Null] Added Vulkan 'window' surface creation via `VK_EXT_headless_surface`
  - [Null] Added EGL context creation on Mesa via `EGL_MESA_platform_surfaceless`
  - [EGL] Allowed native access on Wayland with `GLFW_CONTEXT_CREATION_API` set to

src/x11_monitor.c

@@ -151,6 +151,11 @@ void _glfwPollMonitorsX11(void)
             }
 
             XRRCrtcInfo* ci = XRRGetCrtcInfo(_glfw.x11.display, sr, oi->crtc);
+            if (!ci) {
+                XRRFreeOutputInfo(oi);
+                continue;
+            }
+
             if (ci->rotation == RR_Rotate_90 || ci->rotation == RR_Rotate_270)
             {
                 widthMM  = oi->mm_height;