Merge pull request #1470 from h11128/fix-one-memory-leak

add leak canary dependency and fix one leak

app/build.gradle

@@ -225,4 +225,7 @@ dependencies {
 
     //代码编辑com.github.AmrDeveloper:CodeView已集成到应用内
     //epubLib集成到应用内
+
+    // LeakCanary
+    debugImplementation 'com.squareup.leakcanary:leakcanary-android:2.7'
 }

app/src/main/java/io/legado/app/ui/book/read/ReadBookActivity.kt

@@ -976,6 +976,7 @@ class ReadBookActivity : BaseReadBookActivity(),
         textActionMenu.dismiss()
         binding.readView.onDestroy()
         ReadBook.msg = null
+        ReadBook.callBack = null
         if (!BuildConfig.DEBUG) {
             Backup.autoBack(this)
         }