Add missing space to invalid object error messages

"Invalid tree aa6f10291050a00de83b4630783030b9e3b969ec:duplicate entry names"

is hard to read. A space after the object name and before the message
makes the message more readable.

Change-Id: I96406100dbef8e4bc8fe2047d102681194dc8847

org.eclipse.jgit/resources/org/eclipse/jgit/internal/JGitText.properties

@@ -266,7 +266,7 @@ invalidKey=Invalid key: {0}
 invalidLineInConfigFile=Invalid line in config file
 invalidModeFor=Invalid mode {0} for {1} {2} in {3}.
 invalidModeForPath=Invalid mode {0} for path {1}
-invalidObject=Invalid {0} {1}:{2}
+invalidObject=Invalid {0} {1}: {2}
 invalidOldIdSent=invalid old id sent
 invalidPacketLineHeader=Invalid packet line header: {0}
 invalidPath=Invalid path: {0}