Index: /trunk/src/org/openstreetmap/josm/tools/OsmUrlToBounds.java
===================================================================
--- /trunk/src/org/openstreetmap/josm/tools/OsmUrlToBounds.java	(revision 11846)
+++ /trunk/src/org/openstreetmap/josm/tools/OsmUrlToBounds.java	(revision 11847)
@@ -78,10 +78,9 @@
             } else {
                 String z = map.get("zoom");
-                b = positionToBounds(parseDouble(map, "lat"),
-                        parseDouble(map, "lon"),
+                b = positionToBounds(parseDouble(map, "lat"), parseDouble(map, "lon"),
                         z == null ? 18 : Integer.parseInt(z));
             }
-        } catch (NumberFormatException | ArrayIndexOutOfBoundsException ex) {
-            Main.error(ex);
+        } catch (IllegalArgumentException | ArrayIndexOutOfBoundsException ex) {
+            Main.error(ex, url);
         }
         return b;
@@ -132,5 +131,7 @@
         if (map.containsKey(key))
             return Double.parseDouble(map.get(key));
-        return Double.parseDouble(map.get('m'+key));
+        if (map.containsKey('m'+key))
+            return Double.parseDouble(map.get('m'+key));
+        throw new IllegalArgumentException(map.toString() + " does not contain " + key);
     }