Backport ignoring values outside lightgrid to OpenGL1

Fixes possibly of reading memory past end of lightGridData or reading
wrong light grid data (wrapping around to next row).

code/renderergl1/tr_light.c

@@ -182,6 +182,9 @@ static void R_SetupEntityLightingGrid( trRefEntity_t *ent ) {
 		data = gridData;
 		for ( j = 0 ; j < 3 ; j++ ) {
 			if ( i & (1<<j) ) {
+				if ( pos[j] + 1 > tr.world->lightGridBounds[j] - 1 ) {
+					break; // ignore values outside lightgrid
+				}
 				factor *= frac[j];
 				data += gridStep[j];
 			} else {
@@ -189,6 +192,9 @@ static void R_SetupEntityLightingGrid( trRefEntity_t *ent ) {
 			}
 		}
 
+		if ( j != 3 ) {
+			continue;
+		}
 		if ( !(data[0]+data[1]+data[2]) ) {
 			continue;	// ignore samples in walls
 		}