Ignore task termination when performing searches

When typing quickly, it could happen that two task would be start, and the second would terminate the first, triggering the bug.

Fixes #123

Author: tiennou

Classes/Controllers/PBHistorySearchController.m

@@ -15,6 +15,7 @@
 #import "PBGitDefaults.h"
 #import "PBCommitList.h"
 #import "PBGitCommit.h"
+#import "PBError.h"
 
 @interface PBHistorySearchController ()
 
@@ -420,8 +421,20 @@ - (void)startBackgroundSearch
 	}
 
 	backgroundSearchTask = [historyController.repository taskWithArguments:searchArguments];
-	[backgroundSearchTask performTaskWithCompletionHandler:^(NSData * _Nullable readData, NSError * _Nullable error) {
+	[backgroundSearchTask performTaskWithCompletionHandler:^(NSData *readData, NSError *taskError) {
+		if (taskError.domain == PBTaskErrorDomain && taskError.code == PBTaskCaughtSignalError) {
+			/* Silently ignore task termination */
+			return;
+		}
+
 		if (!readData) {
+			[self clearProgressIndicator];
+			NSString *desc = NSLocalizedString(@"Search failed", @"Search Controller - Background search failed error description");
+			NSString *reason = NSLocalizedString(@"The search for \"%@\" failed.", @"Search Controller - Background search failed error reason");
+			reason = [NSString stringWithFormat:reason, searchString];
+			NSError *error = [NSError pb_errorWithDescription:desc
+												failureReason:reason
+											  underlyingError:taskError];
 			[historyController.windowController showErrorSheet:error];
 			return;
 		}