CMakePM: Filter out (more) empty key configuration items

The code was not filtering empty configuration items
that were the result of bad string input like:
-DMY_KEY:PATH/some/path/but/no/equal/sign

Amends a2a8f56b6e

Task-number: QTCREATORBUG-27237
Change-Id: Ic307eceb66dc0e00b073c9aabb04fe70a223cf08
Reviewed-by: Eike Ziller <eike.ziller@qt.io>

src/plugins/cmakeprojectmanager/cmakeconfigitem.cpp

@@ -349,7 +349,8 @@ CMakeConfig CMakeConfig::fromArguments(const QStringList &list, QStringList &unk
 
         unknownOptions.append(i);
     }
-    return result;
+
+    return Utils::filtered(result, [](const CMakeConfigItem &item) { return !item.key.isEmpty(); });
 }
 
 CMakeConfig CMakeConfig::fromFile(const Utils::FilePath &cacheFile, QString *errorMessage)