fix possible crash

Author: hongxinhope

.gitignore

@@ -0,0 +1 @@
+TBEmptyDataSet.xcworkspace/xcuserdata

Example/Info.plist

@@ -15,11 +15,11 @@
 	<key>CFBundlePackageType</key>
 	<string>APPL</string>
 	<key>CFBundleShortVersionString</key>
-	<string>2.1</string>
+	<string>2.2</string>
 	<key>CFBundleSignature</key>
 	<string>????</string>
 	<key>CFBundleVersion</key>
-	<string>12</string>
+	<string>13</string>
 	<key>LSRequiresIPhoneOS</key>
 	<true/>
 	<key>UILaunchStoryboardName</key>

TBEmptyDataSet/EmptyDataView.swift

@@ -149,14 +149,22 @@ internal class EmptyDataView: UIView {
             var views = [String: UIView]()
 
             if shouldShowImageView() {
+                if imageView.superview == nil {
+                    contentView.addSubview(imageView)
+                }
                 let viewString = ViewStrings.imageView
                 viewStrings.append(viewString)
                 views[viewString] = imageView
 
                 contentView.addConstraint(NSLayoutConstraint(item: imageView, attribute: .centerX, relatedBy: .equal, toItem: contentView, attribute: .centerX, multiplier: 1, constant: 0))
+            } else {
+                imageView.removeFromSuperview()
             }
 
             if shouldShowTitleLabel() {
+                if titleLabel.superview == nil {
+                    contentView.addSubview(titleLabel)
+                }
                 let viewString = ViewStrings.titleLabel
                 viewStrings.append(viewString)
                 views[viewString] = titleLabel
@@ -166,6 +174,9 @@ internal class EmptyDataView: UIView {
             }
 
             if shouldShowDescriptionLabel() {
+                if descriptionLabel.superview == nil {
+                    contentView.addSubview(descriptionLabel)
+                }
                 let viewString = ViewStrings.descriptionLabel
                 viewStrings.append(viewString)
                 views[viewString] = descriptionLabel

TBEmptyDataSet/Supporting Files/Info.plist

@@ -15,7 +15,7 @@
 	<key>CFBundlePackageType</key>
 	<string>FMWK</string>
 	<key>CFBundleShortVersionString</key>
-	<string>2.1</string>
+	<string>2.2</string>
 	<key>CFBundleSignature</key>
 	<string>????</string>
 	<key>CFBundleVersion</key>

TBEmptyDataSetExample.xcodeproj/project.pbxproj

@@ -166,7 +166,7 @@
 			);
 			runOnlyForDeploymentPostprocessing = 0;
 			shellPath = /bin/sh;
-			shellScript = swiftlint;
+			shellScript = "if which swiftlint >/dev/null; then\n    swiftlint\nelse\n    echo \"warning: SwiftLint not installed, download from https://github.com/realm/SwiftLint\"\nfi";
 		};
 /* End PBXShellScriptBuildPhase section */