Prevent crash when adding mpv filter with no name

Ref #2348.  Changes to NewFilterSheetViewController (in FilterWindowController.swift):
* Add button is disabled until text is entered for name of custom mpv filter

iina/Base.lproj/FilterWindowController.xib

@@ -211,6 +211,7 @@ Gw
         </window>
         <viewController id="bda-X5-kCJ" customClass="NewFilterSheetViewController" customModule="IINA" customModuleProvider="target">
             <connections>
+                <outlet property="addButton" destination="THV-Yh-VnK" id="GeO-qk-FbF"/>
                 <outlet property="filterWindow" destination="-2" id="Pjr-CT-nJA"/>
                 <outlet property="scrollContentView" destination="ZHP-RK-Ly4" id="NhJ-gL-sPY"/>
                 <outlet property="tableView" destination="n0t-vk-dME" id="IBk-xT-LkA"/>

iina/FilterWindowController.swift

@@ -299,7 +299,8 @@ class NewFilterSheetViewController: NSViewController, NSTableViewDelegate, NSTab
   @IBOutlet weak var filterWindow: FilterWindowController!
   @IBOutlet weak var tableView: NSTableView!
   @IBOutlet weak var scrollContentView: NSView!
-
+  @IBOutlet weak var addButton: NSButton!
+
   private var currentPreset: FilterPreset?
   private var currentBindings: [String: NSControl] = [:]
   private var presets: [FilterPreset] = []
@@ -333,6 +334,11 @@ class NewFilterSheetViewController: NSViewController, NSTableViewDelegate, NSTab
       self.scrollContentView.addSubview(self.quickLabel(yPos: maxY, title: preset.localizedParamName(name)))
       maxY += 21
       let input = self.quickInput(yPos: &maxY, param: param)
+      // For preventing crash due to adding a filter with no name:
+      if name == "name", preset.name.starts(with: "custom_"), let textField = input as? NSTextField {
+        textField.delegate = self
+        self.addButton.isEnabled = !textField.stringValue.isEmpty
+      }
       self.scrollContentView.addSubview(input)
       self.currentBindings[name] = input
     }
@@ -442,3 +448,12 @@ class NewFilterSheetViewController: NSViewController, NSTableViewDelegate, NSTab
   }
 
 }
+
+/* For preventing crash due to to adding filter with no name */
+extension NewFilterSheetViewController: NSTextFieldDelegate {
+  func controlTextDidChange(_ obj: Notification) {
+    if let textField = obj.object as? NSTextField {
+      self.addButton.isEnabled = !textField.stringValue.isEmpty
+    }
+  }
+}