[java-injection] Fix handling of empty lines in text blocks

GitOrigin-RevId: e3887bb5c7504d925dab62be8b7182a654b2cc0c

java/java-tests/testData/refactoring/replaceConstructorWithFactory/afterInjection.java

@@ -9,6 +9,7 @@ public class Hello {
   void test(@Subst("MyClass") String name, String message) {
     String s = JAVA."""
                 import static java.lang.System.*;
+                
                 class \{name} {
                     private MyClass() {
                     }

java/java-tests/testData/refactoring/replaceConstructorWithFactory/beforeInjection.java

@@ -9,6 +9,7 @@ public class Hello {
   void test(@Subst("MyClass") String name, String message) {
     String s = JAVA."""
                 import static java.lang.System.*;
+
                 <caret>class \{name} {
                     void main(int x) {
                         if (x > 0) {

plugins/IntelliLang/java-support/org/intellij/plugins/intelliLang/inject/java/ConcatenationInjector.java

@@ -436,8 +436,9 @@ public final class ConcatenationInjector implements ConcatenationAwareInjector {
       while (endOffset > 0) {
         endOffset++;
         result.add(new TextRange(startOffset, endOffset));
-        startOffset = endOffset + indent;
-        endOffset = text.indexOf('\n', startOffset);
+        int newEndOffset = text.indexOf('\n', endOffset);
+        startOffset = Math.min(endOffset + indent, newEndOffset == -1 ? Integer.MAX_VALUE : newEndOffset);
+        endOffset = newEndOffset;
       }
       endOffset = textRange.getEndOffset();
       if (startOffset <= endOffset) {