Fixed crash on attempt to load corrupted data file

Instance of FileReader is no longer destructed when header of data file is valid but complete loading of file fails
Loading of truncated .zip file is the simplest test case

src/resourcefiles/file_7z.cpp

@@ -351,6 +351,8 @@ FResourceFile *Check7Z(const char *filename, FileReader *file, bool quiet)
 		{
 			FResourceFile *rf = new F7ZFile(filename, file);
 			if (rf->Open(quiet)) return rf;
+
+			rf->Reader = NULL; // to avoid destruction of reader
 			delete rf;
 		}
 	}

src/resourcefiles/file_grp.cpp

@@ -147,6 +147,8 @@ FResourceFile *CheckGRP(const char *filename, FileReader *file, bool quiet)
 		{
 			FResourceFile *rf = new FGrpFile(filename, file);
 			if (rf->Open(quiet)) return rf;
+
+			rf->Reader = NULL; // to avoid destruction of reader
 			delete rf;
 		}
 	}

src/resourcefiles/file_pak.cpp

@@ -139,6 +139,8 @@ FResourceFile *CheckPak(const char *filename, FileReader *file, bool quiet)
 		{
 			FResourceFile *rf = new FPakFile(filename, file);
 			if (rf->Open(quiet)) return rf;
+
+			rf->Reader = NULL; // to avoid destruction of reader
 			delete rf;
 		}
 	}

src/resourcefiles/file_rff.cpp

@@ -260,6 +260,8 @@ FResourceFile *CheckRFF(const char *filename, FileReader *file, bool quiet)
 		{
 			FResourceFile *rf = new FRFFFile(filename, file);
 			if (rf->Open(quiet)) return rf;
+
+			rf->Reader = NULL; // to avoid destruction of reader
 			delete rf;
 		}
 	}

src/resourcefiles/file_wad.cpp

@@ -651,6 +651,8 @@ FResourceFile *CheckWad(const char *filename, FileReader *file, bool quiet)
 		{
 			FResourceFile *rf = new FWadFile(filename, file);
 			if (rf->Open(quiet)) return rf;
+
+			rf->Reader = NULL; // to avoid destruction of reader
 			delete rf;
 		}
 	}

src/resourcefiles/file_zip.cpp

@@ -423,6 +423,8 @@ FResourceFile *CheckZip(const char *filename, FileReader *file, bool quiet)
 		{
 			FResourceFile *rf = new FZipFile(filename, file);
 			if (rf->Open(quiet)) return rf;
+
+			rf->Reader = NULL; // to avoid destruction of reader
 			delete rf;
 		}
 	}