Allow no-message throwable logging, use `str` for ex-data printing

README.md

@@ -1,7 +1,7 @@
 Current [semantic](http://semver.org/) version:
 
 ```clojure
-[com.taoensso/timbre "2.1.1"] ; See commit history for breaking changes since 1.x
+[com.taoensso/timbre "2.1.2"] ; See commit history for breaking changes since 1.x
 ```
 
 # Timbre, a (sane) Clojure logging & profiling library
@@ -26,7 +26,7 @@ Logging with Java can be maddeningly, unnecessarily hard. Particularly if all yo
 Add the necessary dependency to your [Leiningen](http://leiningen.org/) `project.clj` and `require` the library in your ns:
 
 ```clojure
-[com.taoensso/timbre "2.1.1"] ; project.clj
+[com.taoensso/timbre "2.1.2"] ; project.clj
 (ns my-app (:require [taoensso.timbre :as timbre
                       :refer (trace debug info warn error fatal spy)])) ; ns
 ```

project.clj

@@ -1,4 +1,4 @@
-(defproject com.taoensso/timbre "2.1.1"
+(defproject com.taoensso/timbre "2.1.2"
   :description "Clojure logging & profiling library"
   :url "https://github.com/ptaoussanis/timbre"
   :license {:name "Eclipse Public License"

src/taoensso/timbre.clj

@@ -13,7 +13,7 @@
   "Like `println` but prints all objects to output stream as a single
   atomic string. This is faster and avoids interleaving race conditions."
   [& xs]
-  (print (str (str/join \space xs) \newline))
+  (print (str/join \space (filter identity xs)) \newline)
   (flush))
 
 (defn color-str [color & xs]
@@ -40,8 +40,8 @@
 
 (defn stacktrace [throwable & [separator]]
   (when throwable
-    (str separator (when-let [d (ex-data throwable)] (str d " "))
-         (stacktrace/pst-str throwable))))
+    (str separator throwable ; (str throwable) incl. ex-data for Clojure 1.4+
+         "\n\n" (stacktrace/pst-str throwable))))
 
 ;;;; Default configuration and appenders
 
@@ -326,14 +326,16 @@
   ([base-appender-args level log-args message-fn]
      `(when-let [juxt-fn# (@appenders-juxt-cache ~level)]
         (let [[x1# & xn# :as xs#] (vector ~@log-args)
-              has-throwable?# (and xn# (instance? Throwable x1#))
+              has-throwable?# (instance? Throwable x1#)
               log-vargs# (vec (if has-throwable?# xn# xs#))]
           (log* ~base-appender-args
                 ~level
                 log-vargs#
                 ~(str *ns*)
                 (when has-throwable?# x1#)
-                (when-let [mf# ~message-fn] (apply mf# log-vargs#))
+                (when-let [mf# ~message-fn]
+                  (when-not (empty? log-vargs#)
+                    (apply mf# log-vargs#)))
                 juxt-fn#)))))
 
 (defmacro log