Early exit if the target region is empty

Bug: 193849901
Test: atest StaticLayoutBidiTouchTest
Change-Id: I55f04068a6e5b353867d50742356c272d28886b3
diff --git a/core/java/android/text/TextLine.java b/core/java/android/text/TextLine.java
index 1f11d10..1a7ec7f 100644
--- a/core/java/android/text/TextLine.java
+++ b/core/java/android/text/TextLine.java
@@ -782,7 +782,7 @@
 
         int spanStart = runStart;
         int spanLimit;
-        if (mSpanned == null) {
+        if (mSpanned == null || runStart == runLimit) {
             spanLimit = runLimit;
         } else {
             int target = after ? offset + 1 : offset;