FIX: exists? on not existing URL must return FALSE instead of error

fixes: #14

Author: Oldes

src/mezz/base-files.r

@@ -20,7 +20,9 @@ exists?: func [
 	{Determines if a file or URL exists.}
 	target [file! url!]
 ][
-	not none? query/mode target 'type
+	either error? try [
+		target: query/mode target 'type
+	][	false ][ not none? target ]
 ]
 
 size?: func [

src/tests/units/port-test.r3

@@ -116,6 +116,14 @@ if "true" <> get-env "CONTINUOUS_INTEGRATION" [
 			--assert block?   v: query/mode system/ports/input m
 			--assert 4 = length? v
 	===end-group===
+
+	===start-group=== "HTTP"	
+		--test-- "exists? url"
+			;@@ https://github.com/Oldes/Rebol3/issues/14
+			--assert     exists? http://httpbin.org/
+			--assert not exists? http://httpbin.org/not-exists
+
+	===end-group===
 ]
 
 ~~~end-file~~~