created some tests for ErrorController

src/main/java/org/cryptomator/common/ErrorCode.java

@@ -40,7 +40,7 @@ public class ErrorCode {
 		return format(traceCode(rootCause, rootCauseSpecificFrames));
 	}
 
-	String throwableCode() {
+	public String throwableCode() {
 		return format(traceCode(throwable, ALL_FRAMES));
 	}
 

src/main/java/org/cryptomator/ui/error/ErrorController.java

@@ -151,8 +151,8 @@ public class ErrorController implements FxController {
 		}
 	}
 
-	private boolean isPartialMatchFilter(ErrorDiscussion errorDiscussion) {
-		return errorDiscussion.title.contains(" " +errorCode.methodCode());
+	public boolean isPartialMatchFilter(ErrorDiscussion errorDiscussion) {
+		return errorDiscussion.title.contains(" " + errorCode.methodCode());
 	}
 
 	public int compareUpvoteCount(ErrorDiscussion ed1, ErrorDiscussion ed2) {

src/main/java/org/cryptomator/ui/error/ErrorDiscussion.java

@@ -7,7 +7,8 @@ public class ErrorDiscussion {
 	String url;
 	Answer answer;
 
-	class Answer{
+
+	static class Answer{
 		private String url;
 		private int upvoteCount;
 	}