Do not throw when FileStore cannot create a dir. (#3541)

There is a problem with the file structure on some devices #3269. When we did the FileStore refactor, we turned a silent failure into a runtime exception, causing apps to crash on some of these devices. Although this does not fix the root problem, it reverts to the silent behaviour we had before. We still need to investigate the root cause of this.

Author: mrober

firebase-crashlytics/src/main/java/com/google/firebase/crashlytics/internal/persistence/FileStore.java

@@ -185,7 +185,7 @@ private static synchronized File prepareBaseDir(File file) {
       }
     }
     if (!file.mkdirs()) {
-      throw new IllegalStateException("Could not create Crashlytics-specific directory: " + file);
+      Logger.getLogger().e("Could not create Crashlytics-specific directory: " + file);
     }
     return file;
   }