Fix clipboard paste condition

To avoid possible copy-paste loops between the computer and the device,
the device clipboard is not set if it already contains the expected
content.

But the condition was wrong: it was not set also if it was empty.

Refs 1223a72
Fixes #1658 <#1658>

server/src/main/java/com/genymobile/scrcpy/Device.java

@@ -223,7 +223,7 @@ public boolean setClipboardText(String text) {
         }
 
         String currentClipboard = getClipboardText();
-        if (currentClipboard == null || currentClipboard.equals(text)) {
+        if (currentClipboard != null && currentClipboard.equals(text)) {
             // The clipboard already contains the requested text.
             // Since pasting text from the computer involves setting the device clipboard, it could be set twice on a copy-paste. This would cause
             // the clipboard listeners to be notified twice, and that would flood the Android keyboard clipboard history. To workaround this