patch 8.2.0579: Coverity warns for unused value

Problem:    Coverity warns for unused value.
Solution:   Change order and use "else if".
diff --git a/src/os_unix.c b/src/os_unix.c
index 397342c..c6d386b 100644
--- a/src/os_unix.c
+++ b/src/os_unix.c
@@ -5491,13 +5491,14 @@
 		term = getenv("TERM");
 #endif
 	    // Use 'term' or $TERM if it starts with "xterm", otherwise fall
-	    // back to "xterm".
+	    // back to "xterm" or "xterm-color".
 	    if (term == NULL || *term == NUL || STRNCMP(term, "xterm", 5) != 0)
 	    {
-		if (t_colors > 16)
-		    term = "xterm-color";
 		if (t_colors >= 256)
+		    // TODO: should we check this name is supported?
 		    term = "xterm-256color";
+		else if (t_colors > 16)
+		    term = "xterm-color";
 		else
 		    term = "xterm";
 	    }
diff --git a/src/version.c b/src/version.c
index 2f64d5a..58827f2 100644
--- a/src/version.c
+++ b/src/version.c
@@ -747,6 +747,8 @@
 static int included_patches[] =
 {   /* Add new patch number below this line */
 /**/
+    579,
+/**/
     578,
 /**/
     577,