some more error handling

app/src/main/java/org/wntr/mdeditor/MainActivity.kt

@@ -706,7 +706,7 @@ class MainActivity : AppCompatActivity() {
                     result = cursor.getString(cursor.getColumnIndex(OpenableColumns.DISPLAY_NAME));
                 }
             } finally {
-                cursor!!.close();
+                cursor?.close();
             }
         }
         if (result == null) {
@@ -819,7 +819,7 @@ class MainActivity : AppCompatActivity() {
         try {
             textFile = contentResolver.openFileDescriptor(thisFileUri!!, "w")!!
             textFile.checkError()
-        }catch (e: java.lang.IllegalArgumentException) {
+        } catch (e: java.lang.IllegalArgumentException) {
             Log.d(javaClass.simpleName, "Problem with saving file\nBug in Android 11?\n${e.stackTraceToString()}")
             this.runOnUiThread(
                 {
@@ -834,7 +834,22 @@ class MainActivity : AppCompatActivity() {
             )
             return false
             // TODO: implement workaround for this bug. See: https://stackoverflow.com/q/69248596
-        } catch (e: Exception) {
+        } catch (e: java.io.FileNotFoundException) {
+            Log.d(javaClass.simpleName, "File not found. Deleted while loaded?\n${e.stackTraceToString()}")
+            this.runOnUiThread(
+                {
+                    Toast.makeText(
+                        this,
+                        "File not found. Deleted while loaded?",
+                        Toast.LENGTH_LONG
+                    ).show()
+                }
+            )
+            selectFileForSaveAs()
+            return false
+        }
+
+        catch (e: Exception) {
             Log.d(javaClass.simpleName, "Problem with accessing file\n${e.stackTraceToString()}")
             this.runOnUiThread(
                 {
@@ -960,7 +975,18 @@ class MainActivity : AppCompatActivity() {
                     }
                 }
             }
-        } catch (e: Exception) {
+        } catch (e: java.io.FileNotFoundException) {
+            Log.d(javaClass.simpleName, "File not found during reading:\n${e.stackTraceToString()}")
+            this.runOnUiThread({
+                selectFileForSaveAs()
+                Toast.makeText(
+                    this,
+                    "File not found during reading.\n$e",
+                    Toast.LENGTH_LONG
+                ).show()
+            })
+        }
+        catch (e: Exception) {
             Log.d(javaClass.simpleName, e.stackTraceToString())
             this.runOnUiThread({
                 Toast.makeText(
@@ -969,9 +995,6 @@ class MainActivity : AppCompatActivity() {
                     Toast.LENGTH_LONG
                 ).show()
             })
-/*
-            selectFileForSaveAs()
-*/
             return false
         }