Fail to create GrContext when we get a NULL for a GL/GLSL version string

src/gpu/gl/GrGLAssembleInterface.cpp

Index: src/gpu/gl/GrGLAssembleInterface.cpp
diff --git a/src/gpu/gl/GrGLAssembleInterface.cpp b/src/gpu/gl/GrGLAssembleInterface.cpp
index 11355b8991d65dd5a159599619ce83274ff8123b..aed11e539f74d70674c2830827522f3f50f570af 100644
--- a/src/gpu/gl/GrGLAssembleInterface.cpp
+++ b/src/gpu/gl/GrGLAssembleInterface.cpp
@@ -27,7 +27,7 @@ const GrGLInterface* GrGLAssembleGLInterface(void* ctx, GrGLGetProc get) {
     const char* versionString = (const char*) GetString(GR_GL_VERSION);
     GrGLVersion glVer = GrGLGetVersionFromString(versionString);
 
-    if (glVer < GR_GL_VER(1,5)) {
+    if (glVer < GR_GL_VER(1,5) || GR_GL_INVALID_VER == glVer) {
         // We must have array and element_array buffer objects.
         return NULL;
     }