Added EGL display validity check

If the EGLDisplay input parameter to eglInitialize isn't
PRIMARY_DISPLAY or HEADLESS_DISPLAY, egl::Display::get()
will return null. Instead of crashing, we should return
an EGL_BAD_DISPLAY error.

Change-Id: Ie1e39f2807db5a38f8d21fd6e22270c02cbeba3a
Reviewed-on: https://swiftshader-review.googlesource.com/9813
Tested-by: Alexis Hétu <sugoi@google.com>
Reviewed-by: Nicolas Capens <capn@google.com>

src/OpenGL/libEGL/libEGL.cpp

diff --git a/src/OpenGL/libEGL/libEGL.cpp b/src/OpenGL/libEGL/libEGL.cpp
index 3103abf..0d5f812 100644
--- a/src/OpenGL/libEGL/libEGL.cpp
+++ b/src/OpenGL/libEGL/libEGL.cpp
@@ -133,13 +133,13 @@
 	TRACE("(EGLDisplay dpy = %p, EGLint *major = %p, EGLint *minor = %p)",
 		  dpy, major, minor);
 
-	if(dpy == EGL_NO_DISPLAY)
+	egl::Display *display = egl::Display::get(dpy);
+
+	if(!display)
 	{
 		return error(EGL_BAD_DISPLAY, EGL_FALSE);
 	}
 
-	egl::Display *display = egl::Display::get(dpy);
-
 	if(!display->initialize())
 	{
 		return error(EGL_NOT_INITIALIZED, EGL_FALSE);