util: fix image leak in wmsebg's parseTexture (Coverity #50166)

As pointed by Coverity, in some case of texture with image that needs to
be scaled the temporary scaled image would be leaked if and error occured
during its conversion.

Signed-off-by: Christophe CURIS <christophe.curis@free.fr>

util/wmsetbg.c

@@ -230,6 +230,8 @@ applyImage(RContext * rc, BackgroundTexture * texture, RImage * image, char type
 
 			if (!RConvertImage(rc, image, &pixmap)) {
 				wwarning("could not convert texture:%s", RMessageForError(RErrorCode));
+				if (fimage)
+					RReleaseImage(image);
 				return;
 			}