Bug fix #34174

Multilayer files saved from Maya (and I bet others) store the 'primary' layer without
layer or pass name, just as R G B A. Allows viewers to show stuff too, I guess.

Blender now reads this as well, just allowing an empty string for the layer and pass.

source/blender/imbuf/intern/openexr/openexr_api.cpp

@@ -882,6 +882,12 @@ static int imb_exr_split_channel_name(ExrChannel *echan, char *layname, char *pa
 	const char *token;
 	char tokenbuf[EXR_TOT_MAXNAME];
 	int len;
+	
+	/* some multilayers have the combined buffer with names A B G R saved */
+	if (name[1] == 0) {
+		echan->chan_id = name[0];
+		return 1;
+	}
 
 	/* last token is single character channel identifier */
 	len = imb_exr_split_token(name, end, &token);