Check glGetString for glErrors.

src/renderer_gl.cpp

@@ -2101,7 +2101,7 @@ namespace bgfx
 		if (0 < numCmpFormats)
 		{
 			GLint* formats = (GLint*)alloca(sizeof(GLint)*numCmpFormats);
-			glGetIntegerv(GL_COMPRESSED_TEXTURE_FORMATS, formats);
+			GL_CHECK(glGetIntegerv(GL_COMPRESSED_TEXTURE_FORMATS, formats) );
 
 			for (GLint ii = 0; ii < numCmpFormats; ++ii)
 			{
@@ -2123,6 +2123,7 @@ namespace bgfx
 		GL_GET(GL_MAX_RENDERBUFFER_SIZE, 1);
 
 		const char* version = (const char*)glGetString(GL_SHADING_LANGUAGE_VERSION);
+		GL_CHECK(version = version); // check if error is generated by glGetString.
 		BX_TRACE("GLSL version: %s", version);
 #endif // BGFX_CONFIG_DEBUG