Complete invalid patterns when validating regex during search #2564

If the error is due to an unwritten character at the end of the regex
(e.g. an unescaped trailing backslash) then add a whitespace to avoid
IOOBE.

Fixes #2654

Author: fedejeanne

bundles/org.eclipse.ui/src/org/eclipse/ui/internal/SearchDecoration.java

@@ -83,6 +83,12 @@ private static String buildValidationErrorString(PatternSyntaxException e, Contr
 		GC gc = new GC(targetControl);
 		String pattern = e.getPattern();
 
+		// This happens when the error is in the last (still unwritten) character e.g.
+		// for an "Unescaped trailing backslash"
+		if (errorIndex >= pattern.length()) {
+			pattern += " "; //$NON-NLS-1$
+		}
+
 		StringBuilder validationErrorMessage = new StringBuilder();
 
 		validationErrorMessage.append(description);