patch 8.0.0184: when an error is caught Vim still exits with non-zero result

Problem:    When in Ex mode and an error is caught by try-catch, Vim still
            exits with a non-zero exit code.
Solution:   Don't set ex_exitval when inside a try-catch. (partly by Christian
            Brabandt)

src/message.c

@@ -578,8 +578,6 @@ emsg(char_u *s)
 	return TRUE;
 
     called_emsg = TRUE;
-    if (emsg_silent == 0)
-	ex_exitval = 1;
 
     /*
      * If "emsg_severe" is TRUE: When an error exception is to be thrown,
@@ -642,6 +640,8 @@ emsg(char_u *s)
 	    return TRUE;
 	}
 
+	ex_exitval = 1;
+
 	/* Reset msg_silent, an error causes messages to be switched back on. */
 	msg_silent = 0;
 	cmd_silent = FALSE;