### Eclipse Workspace Patch 1.0
#P josm
diff --git src/org/openstreetmap/josm/gui/help/HelpContentReader.java src/org/openstreetmap/josm/gui/help/HelpContentReader.java
index ce605ca..cebd6e4 100644
--- src/org/openstreetmap/josm/gui/help/HelpContentReader.java
+++ src/org/openstreetmap/josm/gui/help/HelpContentReader.java
@@ -4,6 +4,8 @@
 import java.io.BufferedReader;
 import java.io.IOException;
 import java.net.MalformedURLException;
+import java.net.URI;
+import java.net.URISyntaxException;
 import java.net.URL;
 
 import org.openstreetmap.josm.tools.HttpClient;
@@ -37,22 +39,39 @@
      * @param dotest if {@code true}, checks if help content is empty
      * @return the content, filtered and transformed for being displayed in the internal help browser
      * @throws HelpContentReaderException if problem occurs
-     * @throws MissingHelpContentException if this helpTopicUrl doesn't point to an existing Wiki help page
      */
     public String fetchHelpTopicContent(String helpTopicUrl, boolean dotest) throws HelpContentReaderException {
-        if (helpTopicUrl == null)
-            throw new MissingHelpContentException("helpTopicUrl is null");
+        if (helpTopicUrl == null || helpTopicUrl.isBlank()) {
+            throw new HelpContentReaderException(new IllegalArgumentException("helpTopicUrl is null or blank"), 0);
+        }
         HttpClient.Response con = null;
         try {
-            URL u = new URL(helpTopicUrl);
+            final URL u = new URI(helpTopicUrl).toURL();
             con = HttpClient.create(u).connect();
+            
             try (BufferedReader in = con.getContentReader()) {
                 return prepareHelpContent(in, dotest, u);
             }
-        } catch (MalformedURLException e) {
+        } catch (MalformedURLException | URISyntaxException e) {
             throw new HelpContentReaderException(e, 0);
         } catch (IOException e) {
-            throw new HelpContentReaderException(e, con != null ? con.getResponseCode() : 0);
+            int responseCode = 0;
+            if (con != null) {
+                try {
+                    responseCode = con.getResponseCode();
+                } catch (Exception ignored) {
+                    // do nothing
+                }
+            }
+            throw new HelpContentReaderException(e, responseCode);
+        } finally {
+            if (con instanceof AutoCloseable) {
+                try {
+                    ((AutoCloseable) con).close();
+                } catch (Exception ignored) {
+                    // do nothing
+                }
+            }
         }
     }
 
@@ -78,8 +97,9 @@
         } catch (IOException e) {
             throw new HelpContentReaderException(e, 0);
         }
-        if (dotest && s.isEmpty())
-            throw new MissingHelpContentException(s);
+        if (dotest && s.isEmpty()) {
+            throw new MissingHelpContentException(s);
+        }
         return s;
     }
 }
diff --git test/unit/org/openstreetmap/josm/gui/help/HelpContentReaderTest.java test/unit/org/openstreetmap/josm/gui/help/HelpContentReaderTest.java
index f8f3299..2fc268b 100644
--- test/unit/org/openstreetmap/josm/gui/help/HelpContentReaderTest.java
+++ test/unit/org/openstreetmap/josm/gui/help/HelpContentReaderTest.java
@@ -26,7 +26,7 @@
      */
     @Test
     void testFetchHelpTopicContentNominal() throws HelpContentReaderException {
-        String res = new HelpContentReader(HelpUtil.getWikiBaseUrl()).fetchHelpTopicContent(HelpBrowserTest.URL_1, false);
+        final String res = new HelpContentReader(HelpUtil.getWikiBaseUrl()).fetchHelpTopicContent(HelpBrowserTest.URL_1, false);
         assertFalse(res.isBlank());
     }
 }