Prevent exception when showing injected AsciiDoc content (#1576)

CHANGELOG.adoc

@@ -15,6 +15,7 @@ This document provides a high-level view of the changes introduced by release.
 - Show error popup if a PDF file can't be written to disk (#1569)
 - Quoted strings now highlighted with a background in the editor even if they contain single or double quotes
 - Disable off-screen-rendering if IDE's setting for off-screen-rendering is disabled (#1575)
+- Prevent exception when showing injected AsciiDoc content (#1576)
 
 === 0.41.9
 

src/main/java/org/asciidoc/intellij/psi/AbstractAsciiDocCodeBlock.java

@@ -2,6 +2,8 @@
 
 import com.intellij.lang.ASTNode;
 import com.intellij.navigation.ItemPresentation;
+import com.intellij.openapi.application.ApplicationManager;
+import com.intellij.openapi.util.Computable;
 import com.intellij.openapi.util.TextRange;
 import com.intellij.openapi.util.text.StringUtil;
 import com.intellij.psi.AbstractElementManipulator;
@@ -106,15 +108,17 @@ public String getLocationString() {
 
   @Override
   public boolean isValidHost() {
-    // must not use PsiTreeUtil.findChildOfType as it leads to exception
-    for (PsiElement e : this.getChildren()) {
-      // if there is a block macro (typically an include), disable highlighting for all of it
-      if (e instanceof AsciiDocBlockMacro) {
-        return false;
+    return ApplicationManager.getApplication().runReadAction((Computable<Boolean>) () -> {
+      // must not use PsiTreeUtil.findChildOfType as it leads to exception
+      for (PsiElement e : this.getChildren()) {
+        // if there is a block macro (typically an include), disable highlighting for all of it
+        if (e instanceof AsciiDocBlockMacro) {
+          return false;
+        }
       }
-    }
-    // check if there are i.e. non-matching elements
-    return !getContentTextRange().equals(TextRange.EMPTY_RANGE);
+      // check if there are i.e. non-matching elements
+      return !getContentTextRange().equals(TextRange.EMPTY_RANGE);
+    });
   }
 
   /**