Fix incorrect skipping in contextAttribs parsing in eglCreateContext (library_egl.js)

Fix incorrect skipping of contextAttribs array in eglCreateContext. Otherwise the loop runs twice instead of once, and value will get incorrectly assigned to param, causing glesContextVersion check in eglCreateContext to fail, and return 0x3005.
This line looks odd, and a bit redundant? Same for setting the currentMinorVersion?