java9 tweak (#888)

Author: Jugen

richtextfx/src/main/java9/org/fxmisc/richtext/TextFlowExt.java

@@ -43,9 +43,9 @@ int getLineStartPosition(int charIdx) {
 
     int getLineEndPosition(int charIdx) {
         TwoLevelNavigator navigator = textLayout().getTwoLevelNavigator();
-        int currentLineIndex = navigator.offsetToPosition(charIdx, Forward).getMajor();
-        int minor = (currentLineIndex == getLineCount() - 1) ? 0 : -1;
-        return navigator.position(currentLineIndex + 1, minor).toOffset();
+        int currentLineIndex = navigator.offsetToPosition(charIdx, Forward).getMajor() + 1;
+        int minor = (currentLineIndex == getLineCount()) ? 0 : -1;
+        return navigator.position(currentLineIndex, minor).toOffset();
     }
 
     int getLineOfCharacter(int charIdx) {

richtextfx/src/main/java9/org/fxmisc/richtext/TextFlowLayout.java

@@ -66,7 +66,8 @@ TwoLevelNavigator getTwoLevelNavigator() {
     int getLineCount() {
 
         if ( lineCount > -1 ) return lineCount;
-        
+
+        lineCount = 0;
         lineMetrics.clear();
         double totLines = 0.0, prevMinY = 1.0, prevMaxY = -1.0;
         int totCharSoFar = 0;