chore: Add null check to the Bitbucket Server URL parser (eclipse-che#983)

Author: vinokurig

wsmaster/che-core-api-factory-bitbucket-server/src/main/java/org/eclipse/che/api/factory/server/bitbucket/BitbucketServerURLParser.java

@@ -304,13 +304,17 @@ private BitbucketServerUrl parse(Matcher matcher, @Nullable String revision) {
       project = matcher.group("project");
     }
     String repoName = matcher.group("repo");
-    String branchFromUrl = null;
+    String branch = null;
     try {
-      String branch = matcher.group("branch");
-      branchFromUrl =
-          branch.startsWith("refs/heads/")
-              ? branch.substring(11)
-              : (branch.startsWith("refs%2Fheads%2F") ? branch.substring(15) : branch);
+      String branchFromUrl = matcher.group("branch");
+      if (!isNullOrEmpty(branchFromUrl)) {
+        branch =
+            branchFromUrl.startsWith("refs/heads/")
+                ? branchFromUrl.substring(11)
+                : (branchFromUrl.startsWith("refs%2Fheads%2F")
+                    ? branchFromUrl.substring(15)
+                    : branchFromUrl);
+      }
     } catch (IllegalArgumentException e) {
       // keep branch with null, as the pattern doesn't have the branch group
     }
@@ -322,7 +326,7 @@ private BitbucketServerUrl parse(Matcher matcher, @Nullable String revision) {
         .withProject(project)
         .withUser(user)
         .withRepository(repoName)
-        .withBranch(isNullOrEmpty(branchFromUrl) ? revision : branchFromUrl)
+        .withBranch(isNullOrEmpty(branch) ? revision : branch)
         .withDevfileFilenames(devfileFilenamesProvider.getConfiguredDevfileFilenames());
   }
 }

wsmaster/che-core-api-factory-bitbucket-server/src/test/java/org/eclipse/che/api/factory/server/bitbucket/BitbucketServerURLParserTest.java

@@ -471,6 +471,7 @@ public Object[][] expectedParsing() {
         "repo",
         "branch"
       },
+      {"https://bitbucket.2mcl.com/users/user/repos/repo/browse", "user", null, "repo", null},
       {"https://bbkt.com/users/user/repos/repo/", "user", null, "repo", null}
     };
   }