Android: return String regardless from QtLoader.getMetaData()

To avoid exceptions if the metadata is a non-string like boolean
or integer.

Task-number: QTBUG-115016
Pick-to: 6.7
Change-Id: I104e6b2954873e74bc100cb965ee8ea9b6d14568
Reviewed-by: Janne Juntunen <janne.juntunen@qt.io>
Reviewed-by: Petri Virkkunen <petri.virkkunen@qt.io>
Reviewed-by: Assam Boudjelthia <assam.boudjelthia@qt.io>

src/android/jar/src/org/qtproject/qt/android/QtLoader.java

@@ -300,7 +300,7 @@ abstract class QtLoader {
         if (metadata == null || !metadata.containsKey(key))
             return "";
 
-        return metadata.getString(key);
+        return String.valueOf(metadata.get(key));
     }
 
     @SuppressLint("DiscouragedApi")