CodeQL InconsistentNullnessTest.ql ourgl != NULL

ourgl local variable is set to a non-NULL value (first initialization)
in code that is in lines below where it is dereferenced in a loop.
Somewhere in the loop there is a point where the precondition of ourgl
being set to non-null is expected.
ASSERT added.

graphics/grGlyphs.c

@@ -140,6 +140,8 @@ GrReadGlyphs(filename, path, libPath, gl)
 	    /* an interesting line */
 	    if (sizeline)
 	    {
+		/* this section appears to expect ourgl to be  */
+		ASSERT(ourgl, "ourgl");
 		if (y > 0)
 		    y--; 	/* scan from top down */
 		else